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 | 3 |
| 3 | 18 |
| 4 | 174 |
| 5 | 2370 |
| 6 | 41850 |
| 7 | 908460 |
| 8 | 23393160 |
| 9 | 696752280 |
| 10 | 23558056200 |
| 11 | 891259815600 |
| 12 | 37298874135600 |
| 13 | 1710662148795600 |
| 14 | 85319825069278800 |
| 15 | 4597474487169564000 |
| 16 | 266164417718126928000 |
| 17 | 16475817276720193392000 |