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 | 3 |
| 2 | 15 |
| 3 | 780 |
| 4 | 3828 |
| 5 | 198135 |
| 6 | 972315 |
| 7 | 50325528 |
| 8 | 246964200 |
| 9 | 12782485995 |
| 10 | 62727934503 |
| 11 | 3246701117220 |
| 12 | 15932648399580 |
| 13 | 824649301287903 |
| 14 | 4046829965558835 |
| 15 | 209457675826010160 |
| 16 | 1027878878603544528 |
| 17 | 53201425010505292755 |
| 18 | 261077188335334751295 |
| 19 | 13512952494992518349628 |