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 | 1 |
| 2 | 2 |
| 3 | 9 |
| 4 | 64 |
| 5 | 605 |
| 6 | 6996 |
| 7 | 94556 |
| 8 | 1452928 |
| 9 | 24921765 |
| 10 | 471091360 |
| 11 | 9720039120 |
| 12 | 217285778700 |
| 13 | 5230874655578 |
| 14 | 134929133296972 |
| 15 | 3713182459524270 |
| 16 | 108605754921052880 |
| 17 | 3364866315332574493 |
| 18 | 110099293819641466488 |
| 19 | 3794219154973411079432 |
| 20 | 137375263325254329836460 |