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) |
|---|---|
| 4 | 1 |
| 5 | 10 |
| 6 | 105 |
| 7 | 1295 |
| 8 | 18865 |
| 9 | 320544 |
| 10 | 6258000 |
| 11 | 138437310 |
| 12 | 3428282880 |
| 13 | 94059655690 |
| 14 | 2833936641536 |
| 15 | 93055995703125 |
| 16 | 3308477732618240 |
| 17 | 126642365068676240 |
| 18 | 5193315990469140480 |
| 19 | 227160198500847385884 |
| 20 | 10557603840000000000000 |
| 21 | 519578655591970045435770 |