Starting from zero, each term of the sequence is a(n) = a(n-1) - n
but only if a(n) > 0 and it has not previously generated. In case
the condition doesn't hold, a(n) = a(n-1) + n.
Print the first 250 terms of the sequence one per line.
ARGV is available via STDIN, joined on NULL. x is a no-op.
arguments holds ARGV, print() to output with a newline,
write() to output without a newline.
say() is available without any import.
SELECT arg FROM argv
to access the arguments, only the first
column of the first result set will be printed, NULL values will be
skipped, and the dialect is SQLite