The Calendar hole will go live in approximately 4 days. Why not try and solve it ahead of time?
Collatz in C in bytes. Achievements Cheevos Holes Languages Medals Miscellaneous All Holes 12 Days of Christmas 24 Game 99 Bottles of Beer Abundant Numbers Abundant Numbers (Long) Arabic to Roman Arithmetic Numbers Arrows Ascending Primes ASCII Table Billiards brainfuck Card Number Validation Catalan Numbers Catalan’s Constant Christmas Trees Collatz CSS Colors Cubes Day of Week DFA Simulator Diamonds Divisors Emirp Numbers Emirp Numbers (Long) Emojify Evil Numbers Evil Numbers (Long) Factorial Factorisation Farey Sequence Fibonacci Fizz Buzz Foo Fizz Buzz Bar Forsyth–Edwards Notation Fractions Game of Life Gijswijt’s Sequence Happy Numbers Happy Numbers (Long) Hexdump Hilbert Curve Intersection Inventory Sequence ISBN Jacobi Symbol Kaprekar Numbers Kolakoski Constant Kolakoski Sequence Leap Years Levenshtein Distance Leyland Numbers ln 2 Look and Say Lucky Numbers Lucky Tickets Mahjong Mandelbrot Maze Medal Tally Minesweeper Morse Decoder Morse Encoder Musical Chords N Queens Niven Numbers Niven Numbers (Long) Number Spiral Odious Numbers Odious Numbers (Long) Ordinal Numbers PalindromemordnilaP Pangram Grep Partition Numbers Pascal’s Triangle Pernicious Numbers Pernicious Numbers (Long) Poker Polyominoes Prime Numbers Prime Numbers (Long) Proximity Grid QR Decoder Quine Recamán Repeating Decimals Reverse Polish Notation Reversi Rijndael S-box Rock-paper-scissors-Spock-lizard Roman to Arabic ROT13 Rule 110 Scrambled Sort Set Seven Segment SI Units Sierpiński Triangle Smith Numbers Spelling Numbers Star Wars GPT Star Wars Opening Crawl Sudoku Sudoku (Fill-in) Ten-pin Bowling Tic-tac-toe Time Distance Tongue-twisters Topological Sort Tower of Hanoi Transpose Sentence Trinomial Triangle United States Vampire Numbers Van Eck Sequence Zeckendorf Representation Zodiac Signs γ λ π τ φ √2 𝑒 Apéry’s Constant Binary Lambda Calculus Calendar Connect Four Continued Fractions Crossword CSS Colors (Inverse) CSS Grid Ellipse Perimeters Flags Floyd-Steinberg Dithering Gray Code Decoder Gray Code Encoder Hexagonal Spiral Highly Composite Numbers Multitap Input NFA Simulator Numbrix Odd Polyomino Tiling p-adic Expansion Polygon Triangulations QR Encoder Quadratic Formula Semiprime Numbers Smooth Numbers Snake Sphenic Numbers Taxicab Numbers Turtle Tutorial All Languages ><> Assembly AWK Bash BASIC Berry brainfuck C C# C++ Civet Clojure COBOL Coconut Common Lisp Crystal D Dart Elixir Erlang F# Factor Forth Fortran Gleam Go GolfScript Groovy Haskell Hexagony J Janet Java JavaScript jq Julia K Kotlin Lua Nim OCaml Pascal Perl PHP PowerShell Prolog Python R Raku Rockstar Ruby Rust Scheme sed SQL Swift Tcl TeX V VimL Wren Zig 05AB1E ALGOL 68 APL Arturo Befunge BQN CJam CoffeeScript Egel Fennel Harbour Hare Haxe Hush Hy iogii Knight Luau Odin Picat Qore Racket Rebol Rexx Scala Squirrel Stax Uiua Umka Vala Vyxal Bytes Chars Scoring Bytes Chars Language All ><> Assembly AWK Bash BASIC Berry brainfuck C C# C++ Civet Clojure COBOL Coconut Common Lisp Crystal D Dart Elixir Erlang F# Factor Forth Fortran Gleam Go GolfScript Groovy Haskell Hexagony J Janet Java JavaScript jq Julia K Kotlin Lua Nim OCaml Pascal Perl PHP PowerShell Prolog Python R Raku Rockstar Ruby Rust Scheme sed SQL Swift Tcl TeX V VimL Wren Zig Experimental Language 05AB1E ALGOL 68 APL Arturo Befunge BQN CJam CoffeeScript Egel Fennel Harbour Hare Haxe Hush Hy iogii Knight Luau Odin Picat Qore Racket Rebol Rexx Scala Squirrel Stax Uiua Umka Vala Vyxal Hole All 12 Days of Christmas 24 Game 99 Bottles of Beer Abundant Numbers Abundant Numbers (Long) Arabic to Roman Arithmetic Numbers Arrows Ascending Primes ASCII Table Billiards brainfuck Card Number Validation Catalan Numbers Catalan’s Constant Christmas Trees Collatz CSS Colors Cubes Day of Week DFA Simulator Diamonds Divisors Emirp Numbers Emirp Numbers (Long) Emojify Evil Numbers Evil Numbers (Long) Factorial Factorisation Farey Sequence Fibonacci Fizz Buzz Foo Fizz Buzz Bar Forsyth–Edwards Notation Fractions Game of Life Gijswijt’s Sequence Happy Numbers Happy Numbers (Long) Hexdump Hilbert Curve Intersection Inventory Sequence ISBN Jacobi Symbol Kaprekar Numbers Kolakoski Constant Kolakoski Sequence Leap Years Levenshtein Distance Leyland Numbers ln 2 Look and Say Lucky Numbers Lucky Tickets Mahjong Mandelbrot Maze Medal Tally Minesweeper Morse Decoder Morse Encoder Musical Chords N Queens Niven Numbers Niven Numbers (Long) Number Spiral Odious Numbers Odious Numbers (Long) Ordinal Numbers PalindromemordnilaP Pangram Grep Partition Numbers Pascal’s Triangle Pernicious Numbers Pernicious Numbers (Long) Poker Polyominoes Prime Numbers Prime Numbers (Long) Proximity Grid QR Decoder Quine Recamán Repeating Decimals Reverse Polish Notation Reversi Rijndael S-box Rock-paper-scissors-Spock-lizard Roman to Arabic ROT13 Rule 110 Scrambled Sort Set Seven Segment SI Units Sierpiński Triangle Smith Numbers Spelling Numbers Star Wars GPT Star Wars Opening Crawl Sudoku Sudoku (Fill-in) Ten-pin Bowling Tic-tac-toe Time Distance Tongue-twisters Topological Sort Tower of Hanoi Transpose Sentence Trinomial Triangle United States Vampire Numbers Van Eck Sequence Zeckendorf Representation Zodiac Signs γ λ π τ φ √2 𝑒 Experimental Hole Apéry’s Constant Binary Lambda Calculus Calendar Connect Four Continued Fractions Crossword CSS Colors (Inverse) CSS Grid Ellipse Perimeters Flags Floyd-Steinberg Dithering Gray Code Decoder Gray Code Encoder Hexagonal Spiral Highly Composite Numbers Multitap Input NFA Simulator Numbrix Odd Polyomino Tiling p-adic Expansion Polygon Triangulations QR Encoder Quadratic Formula Semiprime Numbers Smooth Numbers Snake Sphenic Numbers Taxicab Numbers Turtle Tutorial # Golfer Points Bytes Time Submitted 159th mamalakic 739 88 2ms 1 Mar 2023 159th xnacly 🇩🇪 739 88 2ms 5 Jul 2023 159th KrausRaus 🇺🇸 739 88 2ms 31 Jul 2023 159th dranjohn 739 88 3ms 17 Sep 2023 159th roguh 🇬🇹 739 88 2ms 15 Jan 2024 159th northsuperman 739 88 2ms 24 Mar 2024 167th RealAMC 🇳🇿 730 89 2ms 15 Nov 2023 167th mathb0y512 730 89 2ms 25 Jun 2024 167th Mabeloid 🇳🇴 730 89 2ms 25 Sep 2024 170th Starwort 🇬🇧 722 90 2ms 11 Nov 2022 171st astdefu 714 91 2ms 10 Dec 2022 171st msbranicky 714 91 2ms 9 Jan 2024 173rd esseeffeenne 707 92 2ms 6 Jun 2022 173rd MaxElf999 707 92 2ms 5 Feb 2023 173rd ComputerKWasTaken 🇺🇸 707 92 2ms 20 Jan 2025 173rd matejmatik123 🇸🇰 707 92 2ms 6 Jul 2025 177th LawrenceZ1A 🇨🇦 699 93 3ms 25 May 2022 177th jaxmattfair 🇺🇸 699 93 2ms 10 Jan 2023 177th Maximizer02 699 93 2ms 7 May 2024 177th BlueGummi 699 93 2ms 15 Apr 2025 177th 0dyse 699 93 2ms 23 Apr 2025 182nd Smetalo 691 94 2ms 25 Aug 2022 182nd evan18c 691 94 6ms 12 Dec 2023 184th Andrey2001 684 95 2ms 27 Nov 2025 185th kmathis22 677 96 2ms 25 Sep 2025 186th NeatCrown 🇨🇦 670 97 2ms 14 Dec 2022 187th calinous 🇷🇴 663 98 2ms 2 Mar 2023 187th jtaxen 663 98 2ms 14 Apr 2024 189th 6512345 657 99 2ms 8 Nov 2025 190th Azearia 650 100 2ms 6 Jul 2023 191st Sephirem98 637 102 2ms 25 Oct 2023 191st ottav14 637 102 2ms 26 days ago 193rd galloj 🇨🇿 631 103 2ms 20 May 2023 193rd Pyro569 631 103 2ms 28 Jul 2023 195th TornadoCookie 607 107 2ms 17 Oct 2022 195th aarooosh 607 107 2ms 8 Aug 2024 197th dillon-duncando 602 108 2ms 22 Sep 2022 197th blaztoma 🇱🇹 602 108 3ms 18 Nov 2025 199th masflam 596 109 2ms 21 Jun 2024 200th tweska 🇳🇱 591 110 2ms 5 Jun 2023 200th Jaro32768 🇸🇰 591 110 2ms 8 Feb 2024 200th 0xA00 591 110 2ms 24 days ago 203rd michztl01 586 111 2ms 1 Jun 2022 204th kenballus 580 112 2ms 13 Jul 2022 204th nandanjp 580 112 2ms 29 Mar 2023 204th CyberTapir 580 112 2ms 27 Aug 2024 207th Giantnoodlemonster 575 113 2ms 14 Sep 2024 208th pinguicula 570 114 2ms 6 Apr 2023 208th fkantelberg 570 114 2ms 15 Jul 2023 208th Blockyheadman 570 114 2ms 6 Nov 2025 211th TerenceTux 565 115 2ms 22 May 2023 212th tik25 556 117 2ms 28 Mar 2024 213th 104210 542 120 2ms 29 Jul 2022 214th Qruintrox 537 121 2ms 25 Jun 2023 215th aDwarfNamedUrist 533 122 2ms 12 Jul 2023 215th Alex-Huggett 🇬🇧 533 122 2ms 14 Apr 2024 217th cgjohannsen 528 123 2ms 12 Jun 2022 218th TotoAJ 520 125 2ms 15 Dec 2023 218th mrmena 🇦🇺 520 125 2ms 19 Mar 2024 220th StronkCheese 🇺🇸 516 126 2ms 18 Feb 2023 221st MEarley 504 129 2ms 19 Sep 2023 222nd wearsunscreen 489 133 2ms 19 Oct 2023 223rd 4ndyJ 🇬🇧 485 134 2ms 16 Dec 2022 223rd programmeruser2 485 134 2ms 3 Mar 2023 225th AstroOrbis 471 138 3ms 10 Jul 2025 226th julianreece 468 139 2ms 29 Apr 2025 227th myclevorname 🇺🇸 448 145 2ms 20 Aug 2023 228th Bodo171 445 146 2ms 6 Dec 2022 229th jameswmccarty 439 148 2ms 24 Sep 2024 230th craftablescience 417 156 2ms 19 Sep 2023 231st NOS4A5I 411 158 2ms 30 Dec 2022 232nd calum12345 396 164 3ms 27 Mar 2025 233rd george1605 342 190 3ms 14 Feb 2023 234th kevinnaviapaiva 322 202 3ms 20 Feb 2025 235th taha-daneshmand 188 345 3ms 2 Oct 2024 236th MaNafromSaar 169 384 2ms 14 Nov 2023 237th somT-oss 150 432 2ms 26 Nov 2024 238th Haksell 🇦🇶 20 3,242 1ms 28 Feb 2023 239th KatieLG-Transpiler 🇬🇧 15 4,245 1ms 23 Jun 2022 240th KatieLG 🇬🇧 15 4,248 1ms 4 May 2022 First Prev 161–240 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