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 | 2 |
| 1 | 5 |
| 2 | 120 |
| 3 | 1320 |
| 4 | 9240 |
| 5 | 52360 |
| 6 | 52360 |
| 7 | 602140 |
| 8 | 70450380 |
| 9 | 2043061020 |
| 10 | 16344488160 |
| 11 | 3268897632 |
| 12 | 62109055008 |
| 13 | 2546471255328 |
| 14 | 1157486934240 |
| 15 | 54401885909280 |
| 16 | 272009429546400 |
| 17 | 4805499921986400 |
| 18 | 4805499921986400 |
| 19 | 283524495397197600 |
| 20 | 418536159872053600 |