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 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 12 |
| 5 | 60 |
| 6 | 130 |
| 7 | 420 |
| 8 | 8400 |
| 9 | 101080 |
| 10 | 781200 |
| 11 | 4435200 |
| 12 | 37714600 |
| 13 | 607807200 |
| 14 | 8660652000 |
| 15 | 94007313400 |
| 16 | 914497584000 |
| 17 | 11566931376000 |
| 18 | 198256136478400 |
| 19 | 3275456501116800 |
| 20 | 46558791351072000 |
| 21 | 636647461257808000 |
| 22 | 10238792220969312000 |
| 23 | 194852563745775936000 |