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 | 0 |
| 3 | 1 |
| 4 | 5 |
| 5 | 17 |
| 6 | 54 |
| 7 | 177 |
| 8 | 594 |
| 9 | 1997 |
| 10 | 6698 |
| 11 | 22487 |
| 12 | 75701 |
| 13 | 255455 |
| 14 | 863576 |
| 15 | 2923806 |
| 16 | 9913448 |
| 17 | 33658109 |
| 18 | 114417190 |
| 19 | 389385699 |
| 20 | 1326522885 |
| 21 | 4523352061 |
| 22 | 15437800028 |
| 23 | 52730424194 |
| 24 | 180244620903 |
| 25 | 616546133055 |
| 26 | 2110330086114 |
| 27 | 7227665869122 |
| 28 | 24768041790134 |