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 | 2 |
| 3 | 42 |
| 4 | 400 |
| 5 | 2840 |
| 6 | 17376 |
| 7 | 97440 |
| 8 | 516608 |
| 9 | 2634624 |
| 10 | 13058560 |
| 11 | 63320576 |
| 12 | 301707264 |
| 13 | 1417009152 |
| 14 | 6575120384 |
| 15 | 30195425280 |
| 16 | 137430827008 |
| 17 | 620604391424 |
| 18 | 2783097520128 |
| 19 | 12403773407232 |
| 20 | 54975376916480 |
| 21 | 242441862512640 |
| 22 | 1064326263734272 |
| 23 | 4653131038195712 |
| 24 | 20266193591992320 |