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 | 0 |
| 4 | 105 |
| 5 | 109781 |
| 6 | 12597900 |
| 7 | 302280963 |
| 8 | 3356773532 |
| 9 | 23599355991 |
| 10 | 122416062018 |
| 11 | 510681301550 |
| 12 | 1807308075111 |
| 13 | 5622246678741 |
| 14 | 15761274284852 |
| 15 | 40547443860105 |
| 16 | 97044388890450 |
| 17 | 218379097055159 |
| 18 | 465931135430250 |
| 19 | 948922558475388 |
| 20 | 1854955331788517 |
| 21 | 3496355565562725 |