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 | 1 |
| 3 | 8 |
| 4 | 49 |
| 5 | 294 |
| 6 | 1893 |
| 7 | 13572 |
| 8 | 109345 |
| 9 | 985898 |
| 10 | 9863077 |
| 11 | 108503064 |
| 12 | 1302057249 |
| 13 | 16926789294 |
| 14 | 236975148421 |
| 15 | 3554627439308 |
| 16 | 56874039487681 |
| 17 | 966858672273618 |
| 18 | 17403456103022277 |
| 19 | 330665665961879712 |
| 20 | 6613313319247031425 |
| 21 | 138879579704207582870 |