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 | 1 |
| 2 | 5 |
| 3 | 30 |
| 4 | 140 |
| 5 | 420 |
| 6 | 1540 |
| 7 | 4620 |
| 8 | 13860 |
| 9 | 78540 |
| 10 | 157080 |
| 11 | 471240 |
| 12 | 1141140 |
| 13 | 3603600 |
| 14 | 3423420 |
| 15 | 13693680 |
| 16 | 30630600 |
| 17 | 58198140 |
| 18 | 116396280 |
| 19 | 214414200 |
| 20 | 428828400 |
| 21 | 581981400 |
| 22 | 1163962800 |
| 23 | 5354228880 |
| 24 | 4073869800 |
| 25 | 8147739600 |
| 26 | 26771144400 |
| 27 | 36082846800 |
| 28 | 80313433200 |
| 29 | 93699005400 |
| 30 | 187398010800 |