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 | 119 |
| 6 | 694 |
| 7 | 4580 |
| 8 | 33252 |
| 9 | 260202 |
| 10 | 2161837 |
| 11 | 18858720 |
| 12 | 171285237 |
| 13 | 1609282391 |
| 14 | 15561356705 |
| 15 | 154246419725 |
| 16 | 1562151687940 |
| 17 | 16121960812335 |
| 18 | 169178376076607 |
| 19 | 1801800479418116 |
| 20 | 19446010522240384 |
| 21 | 212394673429250090 |
| 22 | 2345064355131025130 |
| 23 | 26148064110299271293 |