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 | 1 |
| 3 | 5 |
| 4 | 22 |
| 5 | 119 |
| 6 | 713 |
| 7 | 5039 |
| 8 | 40296 |
| 9 | 362874 |
| 10 | 3628679 |
| 11 | 39916799 |
| 12 | 479000858 |
| 13 | 6227020799 |
| 14 | 87178286159 |
| 15 | 1307674367875 |
| 16 | 20922789847680 |
| 17 | 355687428095999 |
| 18 | 6402373705364406 |
| 19 | 121645100408831999 |
| 20 | 2432902008173011178 |