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 | 1 |
| 2 | 0 |
| 3 | 3 |
| 4 | 24 |
| 5 | 65 |
| 6 | 480 |
| 7 | 8827 |
| 8 | 72576 |
| 9 | 657729 |
| 10 | 13754880 |
| 11 | 215578451 |
| 12 | 2884992000 |
| 13 | 62280478273 |
| 14 | 1404449120256 |
| 15 | 27032417472075 |
| 16 | 640338738708480 |
| 17 | 17729894860794497 |
| 18 | 453894468727209984 |
| 19 | 12438629293065953059 |