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 | 12 |
| 5 | 120 |
| 6 | 750 |
| 7 | 3780 |
| 8 | 16856 |
| 9 | 69552 |
| 10 | 272250 |
| 11 | 1026300 |
| 12 | 3762132 |
| 13 | 13498056 |
| 14 | 47615750 |
| 15 | 165683700 |
| 16 | 570024240 |
| 17 | 1942538592 |
| 18 | 6566094450 |
| 19 | 22038141420 |
| 20 | 73510278380 |
| 21 | 243854707320 |
| 22 | 804962754750 |
| 23 | 2645408201700 |
| 24 | 8658857196552 |
| 25 | 28237920483600 |
| 26 | 91778694166250 |