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 | -1 |
| 3 | -5 |
| 4 | -15 |
| 5 | -93 |
| 6 | -551 |
| 7 | -4129 |
| 8 | -33607 |
| 9 | -312929 |
| 10 | -3179343 |
| 11 | -35602881 |
| 12 | -432201743 |
| 13 | -5678740945 |
| 14 | -80142780751 |
| 15 | -1210609725905 |
| 16 | -19481112885231 |
| 17 | -332836223507793 |
| 18 | -6016678424942063 |
| 19 | -114746996449871761 |
| 20 | -2302527084416470255 |
| 21 | -48495552665272893329 |