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 | 4 |
| 4 | 39 |
| 5 | 472 |
| 6 | 7255 |
| 7 | 131876 |
| 8 | 2771685 |
| 9 | 66253552 |
| 10 | 1775801814 |
| 11 | 52761229240 |
| 12 | 1721387545471 |
| 13 | 61187851111432 |
| 14 | 2353835271333611 |
| 15 | 97437447411025008 |
| 16 | 4318780849687684325 |
| 17 | 204079128112017902848 |
| 18 | 10241833975586335217950 |
| 19 | 544031400274026445420368 |