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 | 1 |
| 4 | -6 |
| 5 | 35 |
| 6 | -205 |
| 7 | 1204 |
| 8 | -6692 |
| 9 | 29084 |
| 10 | 17160 |
| 11 | -3069924 |
| 12 | 61356724 |
| 13 | -959574408 |
| 14 | 13499619224 |
| 15 | -174983776176 |
| 16 | 2029529618080 |
| 17 | -18417948918640 |
| 18 | 36189097244720 |
| 19 | 4235753092128480 |
| 20 | -157628320980720480 |
| 21 | 4166967770825777280 |
| 22 | -95152715945973322560 |