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 | -6 |
| 3 | 0 |
| 4 | 90 |
| 5 | 0 |
| 6 | -1680 |
| 7 | 0 |
| 8 | 34650 |
| 9 | 0 |
| 10 | -756756 |
| 11 | 0 |
| 12 | 17153136 |
| 13 | 0 |
| 14 | -399072960 |
| 15 | 0 |
| 16 | 9465511770 |
| 17 | 0 |
| 18 | -227873431500 |
| 19 | 0 |
| 20 | 5550996791340 |
| 21 | 0 |
| 22 | -136526995463040 |
| 23 | 0 |
| 24 | 3384731762521200 |
| 25 | 0 |
| 26 | -84478098072866400 |
| 27 | 0 |
| 28 | 2120572665910728000 |
| 29 | 0 |
| 30 | -53494979785374631680 |
| 31 | 0 |