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 | 0 |
| 2 | 0 |
| 3 | 2 |
| 4 | 8 |
| 5 | 37 |
| 6 | 210 |
| 7 | 1380 |
| 8 | 10450 |
| 9 | 89574 |
| 10 | 857351 |
| 11 | 9063434 |
| 12 | 104876887 |
| 13 | 1318452295 |
| 14 | 17893281147 |
| 15 | 260730668150 |
| 16 | 4059948975490 |
| 17 | 67279154450985 |
| 18 | 1182190856781603 |
| 19 | 21954973054515489 |
| 20 | 429690186924088870 |