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) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 9 |
| 5 | 67 |
| 6 | 525 |
| 7 | 4651 |
| 8 | 47229 |
| 9 | 545707 |
| 10 | 7087005 |
| 11 | 102247051 |
| 12 | 1622631549 |
| 13 | 28091565547 |
| 14 | 526858344285 |
| 15 | 10641342962251 |
| 16 | 230283190961469 |
| 17 | 5315654681948587 |
| 18 | 130370767029070365 |
| 19 | 3385534663256714251 |
| 20 | 92801587319328148989 |
| 21 | 2677687796244383678827 |
| 22 | 81124824998504072833245 |
| 23 | 2574844419803190382447051 |