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 | 0 |
| 4 | 1 |
| 5 | 3 |
| 6 | 15 |
| 7 | 91 |
| 8 | 649 |
| 9 | 5253 |
| 10 | 47802 |
| 11 | 482796 |
| 12 | 5359036 |
| 13 | 64844333 |
| 14 | 849460756 |
| 15 | 11977396665 |
| 16 | 180858689642 |
| 17 | 2911824903230 |
| 18 | 49792205845229 |
| 19 | 901238925798638 |
| 20 | 17213663482753993 |
| 21 | 345994636003355265 |
| 22 | 7300486819670796088 |