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 | 6 |
| 3 | 24 |
| 4 | 132 |
| 5 | 500 |
| 6 | 2728 |
| 7 | 10324 |
| 8 | 56651 |
| 9 | 215323 |
| 10 | 1191987 |
| 11 | 4549786 |
| 12 | 25420734 |
| 13 | 97369588 |
| 14 | 548884043 |
| 15 | 2108335364 |
| 16 | 11983465575 |
| 17 | 46136052623 |
| 18 | 264215445322 |
| 19 | 1019173758683 |
| 20 | 5876647410170 |
| 21 | 22705355331214 |
| 22 | 131727633042981 |
| 23 | 509673506069905 |
| 24 | 2973264727753047 |
| 25 | 11518483809430525 |