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 | 1 |
| 2 | 0 |
| 3 | 6 |
| 4 | 4 |
| 5 | 60 |
| 6 | 84 |
| 7 | 700 |
| 8 | 1440 |
| 9 | 8910 |
| 10 | 23100 |
| 11 | 120120 |
| 12 | 360360 |
| 13 | 1684956 |
| 14 | 5552064 |
| 15 | 24302520 |
| 16 | 85101456 |
| 17 | 357502860 |
| 18 | 1302562404 |
| 19 | 5333981796 |
| 20 | 19947127200 |
| 21 | 80408748420 |
| 22 | 305922388200 |
| 23 | 1221485157360 |
| 24 | 4701015343440 |
| 25 | 18664243014300 |