Question: ..., 18, 54, 3, ...
Sample: ..., 1, 1716, 1, ...
Answer: A059025
Sample: ..., 175450, 139759600, 6837625106787, ...
Answer: A011784
Sample:
0, 1, 3, 6, 2, 7,
⋮ 13,
⋮ 20,
23, 12,
10, 22, 11, 21,
Answer: A005132
Keywords: Mathematics, the Online Encyclopedia of Integer Sequences
A133058