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 | 0 |
| 5 | 1 |
| 6 | -4 |
| 7 | 12 |
| 8 | -30 |
| 9 | 70 |
| 10 | -282 |
| 11 | 2195 |
| 12 | -17680 |
| 13 | 122815 |
| 14 | -752054 |
| 15 | 4449773 |
| 16 | -30013564 |
| 17 | 259850583 |
| 18 | -2638753310 |
| 19 | 27217133989 |
| 20 | -269838173334 |
| 21 | 2620588539506 |
| 22 | -26487374528378 |
| 23 | 295615679025264 |
| 24 | -3658718423476721 |