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 | 4 |
| 2 | 145 |
| 3 | 584 |
| 4 | 21169 |
| 5 | 85260 |
| 6 | 3090529 |
| 7 | 12447376 |
| 8 | 451196065 |
| 9 | 1817231636 |
| 10 | 65871534961 |
| 11 | 265303371480 |
| 12 | 9616792908241 |
| 13 | 38732475004444 |
| 14 | 1403985893068225 |
| 15 | 5654676047277344 |
| 16 | 204972323595052609 |
| 17 | 825543970427487780 |
| 18 | 29924555258984612689 |
| 19 | 120523765006365938536 |