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 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 120 |
| 6 | 1800 |
| 7 | 21000 |
| 8 | 235200 |
| 9 | 2693880 |
| 10 | 35947800 |
| 11 | 609615600 |
| 12 | 12504927600 |
| 13 | 281242996320 |
| 14 | 6545492073120 |
| 15 | 155873050569600 |
| 16 | 3849612346944000 |
| 17 | 100588974863402880 |
| 18 | 2818516832681523840 |
| 19 | 84728757269204858880 |
| 20 | 2706516690047188416000 |