This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 144 |
| 6 | 1008 |
| 7 | 8064 |
| 8 | 72576 |
| 9 | 798336 |
| 10 | 9580032 |
| 11 | 124540416 |
| 12 | 1743565824 |
| 13 | 27897053184 |
| 14 | 474249904128 |
| 15 | 8536498274304 |
| 16 | 162193467211776 |
| 17 | 3406062811447296 |
| 18 | 74933381851840512 |
| 19 | 1723467782592331776 |
| 20 | 41363226782215962624 |
| 21 | 1075443896337615028224 |
| 22 | 29036985201115605762048 |