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) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 2 |
| 4 | 23 |
| 5 | 471 |
| 6 | 14189 |
| 7 | 597257 |
| 8 | 33501237 |
| 9 | 2415131467 |
| 10 | 217579283654 |
| 11 | 23953174092058 |
| 12 | 3163948015772640 |
| 13 | 493855720249671680 |
| 14 | 89925233867931779072 |
| 15 | 18892189483975198113792 |
| 16 | 4535777807395775857033216 |