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 | 6 |
| 2 | 30 |
| 3 | 144 |
| 4 | 690 |
| 5 | 3336 |
| 6 | 16290 |
| 7 | 80184 |
| 8 | 396930 |
| 9 | 1972296 |
| 10 | 9823650 |
| 11 | 49003224 |
| 12 | 244667970 |
| 13 | 1222289256 |
| 14 | 6108282210 |
| 15 | 30531894264 |
| 16 | 152630871810 |
| 17 | 763068462216 |
| 18 | 3815084423970 |
| 19 | 19074648065304 |
| 20 | 95370917376450 |
| 21 | 476847616459176 |
| 22 | 2384217167880930 |
| 23 | 11921023089868344 |
| 24 | 59604927188149890 |
| 25 | 298024071132008136 |