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 | 3 |
| 2 | 12 |
| 3 | 72 |
| 4 | 588 |
| 5 | 5652 |
| 6 | 117504 |
| 7 | 1895712 |
| 8 | 46503600 |
| 9 | 839411118 |
| 10 | 25440307200 |
| 11 | 474527311344 |
| 12 | 22404560101168 |
| 13 | 489294047662728 |
| 14 | 30902868417576960 |
| 15 | 1096805935992340800 |
| 16 | 38000593697802058224 |
| 17 | 1318965178069293272496 |
| 18 | 90596485743469636057920 |
| 19 | 3578317312662511683264000 |