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 | 0 |
| 4 | 0 |
| 5 | 1 |
| 6 | 5 |
| 7 | 45 |
| 8 | 385 |
| 9 | 3710 |
| 10 | 38934 |
| 11 | 444990 |
| 12 | 5506710 |
| 13 | 73422855 |
| 14 | 1049946755 |
| 15 | 16035550531 |
| 16 | 260577696015 |
| 17 | 4489954146860 |
| 18 | 81781307674780 |
| 19 | 1570201107355980 |
| 20 | 31698434854748604 |
| 21 | 671260973394676605 |
| 22 | 14879618243581997745 |