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 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 236 |
| 4 | 1034 |
| 5 | 6094 |
| 6 | 40996 |
| 7 | 295740 |
| 8 | 2231022 |
| 9 | 17370163 |
| 10 | 138473536 |
| 11 | 1124433142 |
| 12 | 9266859394 |
| 13 | 77307427741 |
| 14 | 651540030688 |
| 15 | 5538977450256 |
| 16 | 47442103851930 |
| 17 | 409000732566399 |
| 18 | 3546232676711824 |
| 19 | 30903652601552272 |
| 20 | 270529448396053576 |
| 21 | 2377829916885541565 |