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) |
|---|---|
| 2 | 2 |
| 3 | 5 |
| 4 | 23 |
| 5 | 113 |
| 6 | 719 |
| 7 | 5039 |
| 8 | 40289 |
| 9 | 362867 |
| 10 | 3628789 |
| 11 | 39916787 |
| 12 | 479001599 |
| 13 | 6227020777 |
| 14 | 87178291199 |
| 15 | 1307674367953 |
| 16 | 20922789887947 |
| 17 | 355687428095941 |
| 18 | 6402373705727959 |
| 19 | 121645100408831899 |
| 20 | 2432902008176639969 |
| 21 | 51090942171709439969 |
| 22 | 1124000727777607679927 |