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 | 1 |
| 3 | 2 |
| 4 | 5 |
| 5 | 14 |
| 6 | 40 |
| 7 | 127 |
| 8 | 408 |
| 9 | 1364 |
| 10 | 4638 |
| 11 | 16079 |
| 12 | 56401 |
| 13 | 200169 |
| 14 | 716599 |
| 15 | 2585833 |
| 16 | 9392704 |
| 17 | 34319666 |
| 18 | 126046498 |
| 19 | 465076159 |
| 20 | 1723092407 |
| 21 | 6407856762 |
| 22 | 23910255143 |
| 23 | 89493903437 |
| 24 | 335912684824 |
| 25 | 1264106399919 |
| 26 | 4768447977465 |
| 27 | 18027218146451 |