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 | 3 |
| 3 | 11 |
| 4 | 57 |
| 5 | 489 |
| 6 | 5067 |
| 7 | 50595 |
| 8 | 573297 |
| 9 | 9323985 |
| 10 | 168823443 |
| 11 | 2679252795 |
| 12 | 45149256105 |
| 13 | 1121782132665 |
| 14 | 29930127386715 |
| 15 | 629179051311315 |
| 16 | 13329925622622945 |
| 17 | 472248682257228705 |
| 18 | 17395967794618282275 |
| 19 | 434384524558247177835 |
| 20 | 10095605146704332967705 |