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) |
|---|---|
| 2 | 4 |
| 3 | 16 |
| 4 | 120 |
| 5 | 744 |
| 6 | 4922 |
| 7 | 31904 |
| 8 | 208118 |
| 9 | 1354872 |
| 10 | 8826022 |
| 11 | 57483536 |
| 12 | 374412158 |
| 13 | 2438639080 |
| 14 | 15883563110 |
| 15 | 103454037120 |
| 16 | 673825180718 |
| 17 | 4388811619032 |
| 18 | 28585557862518 |
| 19 | 186185731404016 |
| 20 | 1212679737590398 |
| 21 | 7898522254036168 |
| 22 | 51445284278407878 |
| 23 | 335077523213321312 |
| 24 | 2182453613487235150 |
| 25 | 14214930709900240312 |