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 | 0 |
| 1 | 0 |
| 2 | 2 |
| 3 | 6 |
| 4 | 38 |
| 5 | 130 |
| 6 | 662 |
| 7 | 2380 |
| 8 | 11174 |
| 9 | 41226 |
| 10 | 185642 |
| 11 | 695860 |
| 12 | 3055670 |
| 13 | 11576916 |
| 14 | 49995220 |
| 15 | 190876696 |
| 16 | 814610854 |
| 17 | 3128164186 |
| 18 | 13233277634 |
| 19 | 51046844836 |
| 20 | 214488337418 |
| 21 | 830382690556 |
| 22 | 3470405605900 |
| 23 | 13475470680616 |
| 24 | 56073057254198 |
| 25 | 218269673491780 |