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 | 0 |
| 2 | 0 |
| 3 | 4 |
| 4 | 39 |
| 5 | 280 |
| 6 | 1815 |
| 7 | 11284 |
| 8 | 68859 |
| 9 | 416560 |
| 10 | 2509455 |
| 11 | 15086764 |
| 12 | 90610179 |
| 13 | 543928840 |
| 14 | 3264374295 |
| 15 | 19588645444 |
| 16 | 117539063499 |
| 17 | 705255937120 |
| 18 | 4231600258335 |
| 19 | 25389795391324 |
| 20 | 152339353740819 |
| 21 | 914037866361400 |
| 22 | 5484232429393575 |
| 23 | 32905410268988404 |
| 24 | 197432508689714139 |