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 | 0 |
| 1 | 0 |
| 2 | 2 |
| 3 | 9 |
| 4 | 40 |
| 5 | 205 |
| 6 | 1236 |
| 7 | 8659 |
| 8 | 69280 |
| 9 | 623529 |
| 10 | 6235300 |
| 11 | 68588311 |
| 12 | 823059744 |
| 13 | 10699776685 |
| 14 | 149796873604 |
| 15 | 2246953104075 |
| 16 | 35951249665216 |
| 17 | 611171244308689 |
| 18 | 11001082397556420 |
| 19 | 209020565553571999 |
| 20 | 4180411311071440000 |
| 21 | 87788637532500240021 |
| 22 | 1931350025715005280484 |