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 | 1 |
| 3 | 6 |
| 4 | 55 |
| 5 | 660 |
| 6 | 9751 |
| 7 | 170898 |
| 8 | 3463615 |
| 9 | 79669320 |
| 10 | 2050086511 |
| 11 | 58346365110 |
| 12 | 1819621847407 |
| 13 | 61705703989020 |
| 14 | 2260586259354151 |
| 15 | 88971796139662842 |
| 16 | 3743940350046570751 |
| 17 | 167735288431662235920 |
| 18 | 7971302827015366403551 |
| 19 | 400510700317394780627934 |
| 20 | 21212944650652080893863087 |