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 | 1 |
| 2 | 0 |
| 3 | 1 |
| 4 | 2 |
| 5 | 9 |
| 6 | 36 |
| 7 | 154 |
| 8 | 684 |
| 9 | 3128 |
| 10 | 14666 |
| 11 | 70258 |
| 12 | 342766 |
| 13 | 1698625 |
| 14 | 8532410 |
| 15 | 43368153 |
| 16 | 222729492 |
| 17 | 1154455161 |
| 18 | 6033034032 |
| 19 | 31760434883 |
| 20 | 168311948410 |
| 21 | 897327111964 |
| 22 | 4810159375532 |
| 23 | 25914118276362 |