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 | -6 |
| 4 | 37 |
| 5 | 155 |
| 6 | -11616 |
| 7 | 251940 |
| 8 | 783641 |
| 9 | -454238419 |
| 10 | 29895012768 |
| 11 | -757531311386 |
| 12 | -106105977022243 |
| 13 | 21452688824818775 |
| 14 | -2105573104903303616 |
| 15 | 16702280440994303008 |
| 16 | 48278492787774402969521 |
| 17 | -13301912828187822051695559 |
| 18 | 1964564462643243537548661568 |