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 | 8 |
| 2 | 40 |
| 3 | 216 |
| 4 | 980 |
| 5 | 4368 |
| 6 | 18468 |
| 7 | 77520 |
| 8 | 319440 |
| 9 | 1307448 |
| 10 | 5310448 |
| 11 | 21474180 |
| 12 | 86488020 |
| 13 | 347373600 |
| 14 | 1391956192 |
| 15 | 5567901768 |
| 16 | 22239898848 |
| 17 | 88732378800 |
| 18 | 353696824152 |
| 19 | 1408831480056 |
| 20 | 5608231863080 |
| 21 | 22314239255088 |