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 | 12 |
| 3 | 24 |
| 4 | 396 |
| 5 | 2160 |
| 6 | 23160 |
| 7 | 186480 |
| 8 | 1845900 |
| 9 | 17213280 |
| 10 | 171575712 |
| 11 | 1703560320 |
| 12 | 17365421304 |
| 13 | 178323713568 |
| 14 | 1856554560432 |
| 15 | 19487791106784 |
| 16 | 206411964321420 |
| 17 | 2201711191213248 |
| 18 | 23642813637773616 |
| 19 | 255355132936441824 |
| 20 | 2772650461148938656 |