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) |
|---|---|
| 3 | 1 |
| 4 | 8 |
| 5 | 45 |
| 6 | 220 |
| 7 | 1001 |
| 8 | 4368 |
| 9 | 18564 |
| 10 | 77520 |
| 11 | 319770 |
| 12 | 1307504 |
| 13 | 5311735 |
| 14 | 21474180 |
| 15 | 86493225 |
| 16 | 347373600 |
| 17 | 1391975640 |
| 18 | 5567902560 |
| 19 | 22239974430 |
| 20 | 88732378800 |
| 21 | 353697121050 |
| 22 | 1408831480056 |
| 23 | 5608233007146 |
| 24 | 22314239266528 |
| 25 | 88749815264600 |
| 26 | 352870329957600 |
| 27 | 1402659561581460 |