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 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 9 |
| 4 | 60 |
| 5 | 360 |
| 6 | 2040 |
| 7 | 11088 |
| 8 | 58240 |
| 9 | 297216 |
| 10 | 1480320 |
| 11 | 7223040 |
| 12 | 34636800 |
| 13 | 163657728 |
| 14 | 763549696 |
| 15 | 3523645440 |
| 16 | 16107110400 |
| 17 | 73016672256 |
| 18 | 328570011648 |
| 19 | 1468890021888 |
| 20 | 6528375193600 |
| 21 | 28862235279360 |
| 22 | 126993714118656 |