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 | 3 |
| 4 | 0 |
| 5 | 15 |
| 6 | 90 |
| 7 | 210 |
| 8 | 2520 |
| 9 | 13230 |
| 10 | 103950 |
| 11 | 873180 |
| 12 | 7484400 |
| 13 | 72972900 |
| 14 | 745404660 |
| 15 | 8185126950 |
| 16 | 95805309600 |
| 17 | 1184852869200 |
| 18 | 15538995271800 |
| 19 | 214159261516200 |
| 20 | 3109622647131000 |
| 21 | 47252530639314000 |
| 22 | 752635500963746400 |
| 23 | 12499951421009052000 |
| 24 | 216709136059079664000 |