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) |
|---|---|
| 4 | 1 |
| 5 | 10 |
| 6 | 66 |
| 7 | 364 |
| 8 | 1820 |
| 9 | 8568 |
| 10 | 38760 |
| 11 | 170544 |
| 12 | 735471 |
| 13 | 3124550 |
| 14 | 13123110 |
| 15 | 54627300 |
| 16 | 225792840 |
| 17 | 927983760 |
| 18 | 3796297200 |
| 19 | 15471286560 |
| 20 | 62852101650 |
| 21 | 254661927156 |
| 22 | 1029530696964 |
| 23 | 4154246671960 |
| 24 | 16735679449896 |
| 25 | 67327446062800 |
| 26 | 270533919634160 |
| 27 | 1085929983159840 |
| 28 | 4355031703297275 |