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 | 0 |
| 3 | 3 |
| 4 | 6 |
| 5 | 20 |
| 6 | 0 |
| 7 | -126 |
| 8 | -1260 |
| 9 | 3240 |
| 10 | 108360 |
| 11 | 1635480 |
| 12 | 15075720 |
| 13 | 119957760 |
| 14 | 705729024 |
| 15 | 6324040800 |
| 16 | 130989549600 |
| 17 | 3572031415680 |
| 18 | 78736127656320 |
| 19 | 1502102645890560 |
| 20 | 25514633892182400 |
| 21 | 423898384988494080 |
| 22 | 7590291773745542400 |
| 23 | 162254912688831916800 |
| 24 | 4023271392778314673920 |