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 | 1 |
| 4 | 56 |
| 5 | 1326 |
| 6 | 19735 |
| 7 | 221778 |
| 8 | 2074059 |
| 9 | 16957301 |
| 10 | 124727148 |
| 11 | 840130123 |
| 12 | 5244256701 |
| 13 | 30596969639 |
| 14 | 167941891447 |
| 15 | 871758267397 |
| 16 | 4298158203818 |
| 17 | 20204102328683 |
| 18 | 90841311196884 |
| 19 | 391801985882846 |
| 20 | 1625205683251931 |
| 21 | 6498532182528941 |