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 | 2 |
| 4 | 24 |
| 5 | 572 |
| 6 | 21280 |
| 7 | 1074390 |
| 8 | 70299264 |
| 9 | 5792903144 |
| 10 | 587159944704 |
| 11 | 71822748886440 |
| 12 | 10435273503677440 |
| 13 | 1776780701352504408 |
| 14 | 350461958856515690496 |
| 15 | 79284041282799128098778 |
| 16 | 20392765404792755583221760 |
| 17 | 5917934230798152486136427600 |
| 18 | 1924427226324694427836833857536 |