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) |
|---|---|
| 1 | 4 |
| 2 | 6 |
| 3 | 15 |
| 4 | 105 |
| 5 | 5460 |
| 6 | 14903070 |
| 7 | 111050740260915 |
| 8 | 6166133456248548335768188155 |
| 9 | 19010600900133834176644234577571914951562754277857057935 |