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 | 1 |
| 4 | 3 |
| 5 | 9 |
| 6 | 33 |
| 7 | 135 |
| 8 | 609 |
| 9 | 2985 |
| 10 | 15747 |
| 11 | 88761 |
| 12 | 531561 |
| 13 | 3366567 |
| 14 | 22462017 |
| 15 | 157363329 |
| 16 | 1154257683 |
| 17 | 8841865833 |
| 18 | 70573741857 |
| 19 | 585753925047 |
| 20 | 5046128460801 |
| 21 | 45044554041897 |
| 22 | 416005748766771 |
| 23 | 3969321053484921 |
| 24 | 39077616720410409 |