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) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 8 |
| 6 | 36 |
| 7 | 160 |
| 8 | 548 |
| 9 | 1920 |
| 10 | 6496 |
| 11 | 23040 |
| 12 | 84565 |
| 13 | 317440 |
| 14 | 1197824 |
| 15 | 4508328 |
| 16 | 16905344 |
| 17 | 63406080 |
| 18 | 238602228 |
| 19 | 902430720 |
| 20 | 3429249843 |
| 21 | 13076616480 |
| 22 | 49977704448 |
| 23 | 191312691200 |
| 24 | 733365135860 |
| 25 | 2815436626328 |
| 26 | 10825959342080 |
| 27 | 41694904974720 |
| 28 | 160823207301705 |