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 | 3 |
| 3 | 5 |
| 4 | -60 |
| 5 | -186 |
| 6 | 13832 |
| 7 | -98862 |
| 8 | -8631360 |
| 9 | 352796880 |
| 10 | 4245955032 |
| 11 | -1185349047048 |
| 12 | 48595690153920 |
| 13 | 3201334718188320 |
| 14 | -607575977909763840 |
| 15 | 26489851912606455504 |
| 16 | 4482546578798646251520 |
| 17 | -958939334596403708474880 |
| 18 | 50300999315063602037775360 |
| 19 | 14223928928980522264922223360 |
| 20 | -3933112779003946549567400925696 |