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) |
|---|---|
| 2 | 1 |
| 3 | 6 |
| 4 | 28 |
| 5 | 120 |
| 6 | 495 |
| 7 | 2002 |
| 8 | 8008 |
| 9 | 31824 |
| 10 | 125970 |
| 11 | 497420 |
| 12 | 1961256 |
| 13 | 7726160 |
| 14 | 30421755 |
| 15 | 119759850 |
| 16 | 471435600 |
| 17 | 1855967520 |
| 18 | 7307872110 |
| 19 | 28781143380 |
| 20 | 113380261800 |
| 21 | 446775310800 |
| 22 | 1761039350070 |
| 23 | 6943526580276 |
| 24 | 27385657281648 |
| 25 | 108043253365600 |