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 | 0 |
| 2 | 1 |
| 3 | 60 |
| 4 | 0 |
| 5 | 0 |
| 6 | 19958400 |
| 7 | 0 |
| 8 | 0 |
| 9 | 622452999168000 |
| 10 | 0 |
| 11 | 0 |
| 12 | 258520167388849766400000 |
| 13 | 0 |
| 14 | 0 |
| 15 | 675289572271869736778268672000000 |
| 16 | 0 |
| 17 | 0 |
| 18 | 7393367369949286697176489031997849600000000 |
| 19 | 0 |
| 20 | 0 |