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 | 8 |
| 3 | 40 |
| 4 | 312 |
| 5 | 2240 |
| 6 | 17280 |
| 7 | 134568 |
| 8 | 1071000 |
| 9 | 8627872 |
| 10 | 70302888 |
| 11 | 577920200 |
| 12 | 4786740112 |
| 13 | 39899052960 |
| 14 | 334391846048 |
| 15 | 2815803070920 |
| 16 | 23809393390680 |
| 17 | 202061204197632 |
| 18 | 1720404406215720 |
| 19 | 14690717541313128 |
| 20 | 125775000062934552 |