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 | 0 |
| 3 | -5 |
| 4 | -15 |
| 5 | 104 |
| 6 | 1827 |
| 7 | 7893 |
| 8 | -207000 |
| 9 | -5646249 |
| 10 | -47897675 |
| 11 | 1479282600 |
| 12 | 74711288407 |
| 13 | 1396956334921 |
| 14 | -21032523700672 |
| 15 | -2719998717430365 |
| 16 | -104158663871982343 |
| 17 | -715846242343471272 |
| 18 | 189941380201812700699 |
| 19 | 14820744271258596866013 |
| 20 | 507768838531742620183176 |