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 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 3 |
| 5 | 8 |
| 6 | 36 |
| 7 | 110 |
| 8 | 666 |
| 9 | 3250 |
| 10 | 23436 |
| 11 | 125198 |
| 12 | 1037520 |
| 13 | 7241272 |
| 14 | 66360960 |
| 15 | 500827928 |
| 16 | 5080370400 |
| 17 | 45926666984 |
| 18 | 508032504000 |
| 19 | 4919789029480 |
| 20 | 59256857923200 |
| 21 | 656763542278304 |
| 22 | 8532986822438400 |
| 23 | 100525959568386848 |
| 24 | 1405335514253932800 |
| 25 | 18431883489984091552 |