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) |
|---|---|
| 1 | 1 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 2 |
| 6 | 0 |
| 7 | 0 |
| 8 | 10 |
| 9 | 36 |
| 10 | 0 |
| 11 | 0 |
| 12 | 720 |
| 13 | 5600 |
| 14 | 0 |
| 15 | 0 |
| 16 | 703760 |
| 17 | 11220000 |
| 18 | 0 |
| 19 | 0 |
| 20 | 9168331776 |
| 21 | 293293716992 |
| 22 | 0 |
| 23 | 0 |
| 24 | 1601371799340544 |
| 25 | 102484848265030656 |
| 26 | 0 |
| 27 | 0 |
| 28 | 3837878966366932639744 |
| 29 | 491247277315343649710080 |
| 30 | 0 |
| 31 | 0 |