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) |
|---|---|
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 12 |
| 6 | 72 |
| 7 | 612 |
| 8 | 3552 |
| 9 | 34632 |
| 10 | 247824 |
| 11 | 3047544 |
| 12 | 26502624 |
| 13 | 396071604 |
| 14 | 4055072664 |
| 15 | 71316639036 |
| 16 | 839706878016 |
| 17 | 16982482829136 |
| 18 | 225984627860256 |
| 19 | 5165674068939696 |
| 20 | 76644407669629248 |
| 21 | 1953726395279874588 |
| 22 | 31974794507569558248 |
| 23 | 899186672783502993108 |
| 24 | 16089847137602083031328 |