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 | 0 |
| 4 | 4 |
| 5 | 0 |
| 6 | 0 |
| 7 | 70 |
| 8 | 1120 |
| 9 | 0 |
| 10 | 2800 |
| 11 | 184800 |
| 12 | 2217600 |
| 13 | 200200 |
| 14 | 39239200 |
| 15 | 1513512000 |
| 16 | 16166550400 |
| 17 | 11435424000 |
| 18 | 1029188160000 |
| 19 | 31290941281600 |
| 20 | 317363510464000 |
| 21 | 821292151680000 |
| 22 | 52198475641312000 |
| 23 | 1387554839326656000 |
| 24 | 14092570281613824000 |
| 25 | 92349968764253200000 |