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 | -2 |
| 3 | -3 |
| 4 | 8 |
| 5 | 95 |
| 6 | 684 |
| 7 | 4991 |
| 8 | 40256 |
| 9 | 362799 |
| 10 | 3628700 |
| 11 | 39916679 |
| 12 | 479001456 |
| 13 | 6227020631 |
| 14 | 87178291004 |
| 15 | 1307674367775 |
| 16 | 20922789887744 |
| 17 | 355687428095711 |
| 18 | 6402373705727676 |
| 19 | 121645100408831639 |
| 20 | 2432902008176639600 |
| 21 | 51090942171709439559 |
| 22 | 1124000727777607679516 |