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 | 0 |
| 3 | 1 |
| 4 | 2 |
| 5 | 6 |
| 6 | 17 |
| 7 | 57 |
| 8 | 191 |
| 9 | 663 |
| 10 | 2415 |
| 11 | 9108 |
| 12 | 35695 |
| 13 | 143989 |
| 14 | 599802 |
| 15 | 2566917 |
| 16 | 11298164 |
| 17 | 50967216 |
| 18 | 235745644 |
| 19 | 1115324000 |
| 20 | 5397332497 |
| 21 | 26669487517 |
| 22 | 134528555379 |
| 23 | 691856601631 |
| 24 | 3626390958551 |
| 25 | 19353306241764 |
| 26 | 105122093620388 |
| 27 | 580689432523534 |
| 28 | 3260906342453966 |