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 | 1 |
| 2 | 3 |
| 3 | 10 |
| 4 | 45 |
| 5 | 246 |
| 6 | 1596 |
| 7 | 11472 |
| 8 | 96768 |
| 9 | 905760 |
| 10 | 9282240 |
| 11 | 104328000 |
| 12 | 1285502400 |
| 13 | 17030200320 |
| 14 | 242650598400 |
| 15 | 3685666037760 |
| 16 | 60059908823040 |
| 17 | 1032474885120000 |
| 18 | 18781151090688000 |
| 19 | 360710540426880000 |
| 20 | 7302919022138880000 |
| 21 | 154603891182698496000 |
| 22 | 3423234952360194048000 |