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 | 5 |
| 3 | 30 |
| 4 | 201 |
| 5 | 1445 |
| 6 | 10900 |
| 7 | 85128 |
| 8 | 682505 |
| 9 | 5585115 |
| 10 | 46461437 |
| 11 | 391743850 |
| 12 | 3340361700 |
| 13 | 28755475180 |
| 14 | 249572076200 |
| 15 | 2181469638880 |
| 16 | 19186562661273 |
| 17 | 169677521094215 |
| 18 | 1507881643936015 |
| 19 | 13458730170115778 |
| 20 | 120599648894147185 |