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 | 120 |
| 6 | 565 |
| 7 | 2473 |
| 8 | 10468 |
| 9 | 44148 |
| 10 | 187363 |
| 11 | 799605 |
| 12 | 3418967 |
| 13 | 14615713 |
| 14 | 62439735 |
| 15 | 266643093 |
| 16 | 1138577340 |
| 17 | 4862025964 |
| 18 | 20763336212 |
| 19 | 88672294260 |
| 20 | 378685960241 |
| 21 | 1617214869969 |
| 22 | 6906440938924 |
| 23 | 29494450730730 |
| 24 | 125958207787945 |
| 25 | 537914052728909 |