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 | 0 |
| 2 | 6 |
| 3 | 36 |
| 4 | 252 |
| 5 | 1728 |
| 6 | 11880 |
| 7 | 81648 |
| 8 | 561168 |
| 9 | 3856896 |
| 10 | 26508384 |
| 11 | 182191680 |
| 12 | 1252200384 |
| 13 | 8606352384 |
| 14 | 59151316608 |
| 15 | 406546013952 |
| 16 | 2794183983360 |
| 17 | 19204379983872 |
| 18 | 131991383803392 |
| 19 | 907174582723584 |
| 20 | 6234995799161856 |