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 | 3 |
| 3 | 24 |
| 4 | 165 |
| 5 | 1104 |
| 6 | 7347 |
| 7 | 48840 |
| 8 | 324597 |
| 9 | 2157216 |
| 10 | 14336355 |
| 11 | 95275896 |
| 12 | 633179973 |
| 13 | 4207956720 |
| 14 | 27965034003 |
| 15 | 185848661544 |
| 16 | 1235103986325 |
| 17 | 8208193936704 |
| 18 | 54549615616707 |
| 19 | 362523179503320 |
| 20 | 2409238895476197 |
| 21 | 16011202548279696 |