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 | 1 |
| 2 | 0 |
| 3 | 3 |
| 4 | 12 |
| 5 | 80 |
| 6 | 840 |
| 7 | 4032 |
| 8 | 31976 |
| 9 | 371016 |
| 10 | 4354650 |
| 11 | 55066880 |
| 12 | 680003412 |
| 13 | 9047989392 |
| 14 | 132626606294 |
| 15 | 2096065474440 |
| 16 | 34991505975120 |
| 17 | 607163217989312 |
| 18 | 11006996786618994 |
| 19 | 209218563659672064 |
| 20 | 4168806234781798100 |
| 21 | 86745911047924139760 |
| 22 | 1876774293382882814382 |