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 | 5 |
| 2 | 45 |
| 3 | 407 |
| 4 | 3411 |
| 5 | 25142 |
| 6 | 163711 |
| 7 | 947909 |
| 8 | 4949257 |
| 9 | 23579022 |
| 10 | 103592423 |
| 11 | 423435205 |
| 12 | 1622413728 |
| 13 | 5864055622 |
| 14 | 20102107500 |
| 15 | 65660463140 |
| 16 | 205176581382 |
| 17 | 615506305973 |
| 18 | 1778086106680 |
| 19 | 4959845850882 |
| 20 | 13391444267162 |
| 21 | 35072585737475 |
| 22 | 89275252614236 |
| 23 | 221246652070184 |