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 | -1 |
| 2 | -2 |
| 3 | 3 |
| 4 | 14 |
| 5 | 45 |
| 6 | -156 |
| 7 | -1225 |
| 8 | -3396 |
| 9 | -105 |
| 10 | 226760 |
| 11 | 1175229 |
| 12 | 4084200 |
| 13 | -35683219 |
| 14 | -585896962 |
| 15 | -3512021955 |
| 16 | -14398868176 |
| 17 | 198247498911 |
| 18 | 3131185307832 |
| 19 | 29821940715413 |
| 20 | 122481857683680 |
| 21 | -1187008881417051 |
| 22 | -31616420134183522 |
| 23 | -419944298964036771 |