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 | 1 |
| 2 | 2 |
| 3 | 9 |
| 4 | 64 |
| 5 | 505 |
| 6 | 4536 |
| 7 | 46249 |
| 8 | 526352 |
| 9 | 6604497 |
| 10 | 90466480 |
| 11 | 1341571561 |
| 12 | 21392282088 |
| 13 | 364715915161 |
| 14 | 6616327512536 |
| 15 | 127187163197865 |
| 16 | 2581443127409056 |
| 17 | 55143025567270561 |
| 18 | 1236226458392407008 |
| 19 | 29012548251081127753 |
| 20 | 711157579030313374520 |
| 21 | 18169564436494014726441 |