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 | 1 |
| 2 | 10 |
| 3 | 505 |
| 4 | 33670 |
| 5 | 2457190 |
| 6 | 189442252 |
| 7 | 15177798415 |
| 8 | 1251216059950 |
| 9 | 105443928375598 |
| 10 | 9043123211156440 |
| 11 | 786701771691580227 |
| 12 | 69253844083218535300 |
| 13 | 6157639918607211895000 |
| 14 | 552193624489443516667344 |
| 15 | 49885368826043082235592687 |