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) |
|---|---|
| 1 | 12 |
| 2 | 124 |
| 3 | 780 |
| 4 | 7812 |
| 5 | 33624 |
| 6 | 354640 |
| 7 | 1704240 |
| 8 | 18929096 |
| 9 | 97036800 |
| 10 | 800520192 |
| 11 | 3958188480 |
| 12 | 56928231360 |
| 13 | 193778020824 |
| 14 | 1830926384640 |
| 15 | 11181115146240 |
| 16 | 115997032277280 |
| 17 | 465294239722800 |
| 18 | 5175558387507200 |
| 19 | 22852200371636160 |
| 20 | 287850454432579584 |
| 21 | 1318081737957660000 |