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 | 2 |
| 2 | 10 |
| 3 | 84 |
| 4 | 1008 |
| 5 | 15840 |
| 6 | 308880 |
| 7 | 7207200 |
| 8 | 196035840 |
| 9 | 6094932480 |
| 10 | 213322636800 |
| 11 | 8303173401600 |
| 12 | 355850288640000 |
| 13 | 16653793508352000 |
| 14 | 845180020548864000 |
| 15 | 46236318771202560000 |
| 16 | 2712530701243883520000 |
| 17 | 169890080762116915200000 |
| 18 | 11314679378756986552320000 |