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 | 0 |
| 1 | 1 |
| 2 | 20 |
| 3 | 361 |
| 4 | 6480 |
| 5 | 116281 |
| 6 | 2086580 |
| 7 | 37442161 |
| 8 | 671872320 |
| 9 | 12056259601 |
| 10 | 216340800500 |
| 11 | 3882078149401 |
| 12 | 69661065888720 |
| 13 | 1250017107847561 |
| 14 | 22430646875367380 |
| 15 | 402501626648765281 |
| 16 | 7222598632802407680 |
| 17 | 129604273763794572961 |
| 18 | 2325654329115499905620 |