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 | 1 |
| 1 | 0 |
| 2 | 2 |
| 3 | 3 |
| 4 | 24 |
| 5 | 125 |
| 6 | 900 |
| 7 | 7987 |
| 8 | 72240 |
| 9 | 817488 |
| 10 | 9536940 |
| 11 | 127816931 |
| 12 | 1830739680 |
| 13 | 28597812685 |
| 14 | 481145656992 |
| 15 | 8650951895040 |
| 16 | 166376275228800 |
| 17 | 3392537585542577 |
| 18 | 73342277086465296 |
| 19 | 1672523286398099407 |
| 20 | 40158685461798481560 |
| 21 | 1012415090497566344400 |