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 | 3 |
| 4 | 0 |
| 5 | 15 |
| 6 | 180 |
| 7 | 105 |
| 8 | 5040 |
| 9 | 46305 |
| 10 | 132300 |
| 11 | 3752595 |
| 12 | 33679800 |
| 13 | 243378135 |
| 14 | 5565940380 |
| 15 | 56191160025 |
| 16 | 712410098400 |
| 17 | 14889814164225 |
| 18 | 183558878603100 |
| 19 | 3236148386145675 |
| 20 | 66650136566013000 |
| 21 | 1027807726886515575 |
| 22 | 21983938825036488300 |
| 23 | 469896981350215644225 |