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 | 63 |
| 6 | 412 |
| 7 | 2673 |
| 8 | 17571 |
| 9 | 117365 |
| 10 | 798819 |
| 11 | 5530122 |
| 12 | 38908380 |
| 13 | 277750749 |
| 14 | 2009160864 |
| 15 | 14707923021 |
| 16 | 108835512411 |
| 17 | 813241695330 |
| 18 | 6130521151377 |
| 19 | 46584949832013 |
| 20 | 356571373433217 |
| 21 | 2747371943624943 |
| 22 | 21296479544449677 |
| 23 | 165994877608025730 |
| 24 | 1300408539157086640 |