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 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 54 |
| 5 | 780 |
| 6 | 7830 |
| 7 | 67620 |
| 8 | 535374 |
| 9 | 3992940 |
| 10 | 28483110 |
| 11 | 196316340 |
| 12 | 1317106494 |
| 13 | 8650141500 |
| 14 | 55853351190 |
| 15 | 355770438660 |
| 16 | 2241509994414 |
| 17 | 13998294536460 |
| 18 | 86795899256070 |
| 19 | 535048203626580 |
| 20 | 3282628800655134 |
| 21 | 20061393719417820 |
| 22 | 122212221633141750 |