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 | 1 |
| 2 | 3 |
| 3 | 15 |
| 4 | 105 |
| 5 | 1155 |
| 6 | 15015 |
| 7 | 255255 |
| 8 | 4849845 |
| 9 | 111546435 |
| 10 | 3234846615 |
| 11 | 100280245065 |
| 12 | 3710369067405 |
| 13 | 152125131763605 |
| 14 | 6541380665835015 |
| 15 | 307444891294245705 |
| 16 | 16294579238595022365 |
| 17 | 961380175077106319535 |
| 18 | 58644190679703485491635 |
| 19 | 3929160775540133527939545 |
| 20 | 278970415063349480483707695 |