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 | 0 |
| 2 | 4 |
| 3 | 0 |
| 4 | 52 |
| 5 | 194 |
| 6 | 808 |
| 7 | 2858 |
| 8 | 13998 |
| 9 | 66154 |
| 10 | 378268 |
| 11 | 1550370 |
| 12 | 7987672 |
| 13 | 37394810 |
| 14 | 190191026 |
| 15 | 958595712 |
| 16 | 4634180280 |
| 17 | 23153016922 |
| 18 | 114436235324 |
| 19 | 570764742248 |
| 20 | 2855728422214 |
| 21 | 14134719577328 |
| 22 | 70532689287114 |
| 23 | 350910293711340 |
| 24 | 1748728132235334 |
| 25 | 8722708834873854 |