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 | 1 |
| 3 | 2 |
| 4 | 5 |
| 5 | 16 |
| 6 | 56 |
| 7 | 204 |
| 8 | 768 |
| 9 | 2970 |
| 10 | 11726 |
| 11 | 47060 |
| 12 | 191412 |
| 13 | 787304 |
| 14 | 3269100 |
| 15 | 13684864 |
| 16 | 57691353 |
| 17 | 244713654 |
| 18 | 1043684478 |
| 19 | 4472828400 |
| 20 | 19252045120 |
| 21 | 83188965420 |
| 22 | 360734837280 |
| 23 | 1569296837160 |
| 24 | 6846931211250 |
| 25 | 29954007587556 |
| 26 | 131367797081352 |
| 27 | 577451514567536 |