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 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 11 |
| 5 | 87 |
| 6 | 640 |
| 7 | 4855 |
| 8 | 39909 |
| 9 | 361995 |
| 10 | 3626938 |
| 11 | 39912947 |
| 12 | 478993719 |
| 13 | 6227004807 |
| 14 | 87178258916 |
| 15 | 1307674303055 |
| 16 | 20922789757641 |
| 17 | 355687427834707 |
| 18 | 6402373705204718 |
| 19 | 121645100407784603 |
| 20 | 2432902008174544219 |