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 | 0 |
| 3 | 0 |
| 4 | 2 |
| 5 | 24 |
| 6 | 228 |
| 7 | 2088 |
| 8 | 19732 |
| 9 | 197890 |
| 10 | 2131060 |
| 11 | 24729108 |
| 12 | 309027560 |
| 13 | 4148115048 |
| 14 | 59611031304 |
| 15 | 913915160628 |
| 16 | 14897443573244 |
| 17 | 257369478424890 |
| 18 | 4698494631208500 |
| 19 | 90393611677083892 |
| 20 | 1828153614233855024 |
| 21 | 38778554791649355232 |
| 22 | 860921156414834534368 |