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 | 9 |
| 3 | 45 |
| 4 | 285 |
| 5 | 1575 |
| 6 | 9237 |
| 7 | 52221 |
| 8 | 297633 |
| 9 | 1676364 |
| 10 | 9425128 |
| 11 | 52688379 |
| 12 | 293582296 |
| 13 | 1629482947 |
| 14 | 9015732880 |
| 15 | 49727160669 |
| 16 | 273504111761 |
| 17 | 1500271605182 |
| 18 | 8209029290412 |
| 19 | 44811239964075 |
| 20 | 244069307558722 |
| 21 | 1326536980923855 |
| 22 | 7195340066129605 |
| 23 | 38953817605037254 |