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 | 1 |
| 2 | 2 |
| 3 | 9 |
| 4 | 56 |
| 5 | 465 |
| 6 | 4764 |
| 7 | 58345 |
| 8 | 830192 |
| 9 | 13466817 |
| 10 | 245254580 |
| 11 | 4955259441 |
| 12 | 109995693576 |
| 13 | 2661003245329 |
| 14 | 69682488950060 |
| 15 | 1963774182830265 |
| 16 | 59261538449833184 |
| 17 | 1906643335934717697 |
| 18 | 65149411890671521380 |
| 19 | 2356212733788818122561 |
| 20 | 89920484394446094721400 |