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 | 6 |
| 2 | -6 |
| 3 | 1428 |
| 4 | -13146 |
| 5 | 280788 |
| 6 | -3785820 |
| 7 | 93142824 |
| 8 | -1851272826 |
| 9 | 37533646212 |
| 10 | -765409050420 |
| 11 | 16617464296728 |
| 12 | -357906128318628 |
| 13 | 7730398360992840 |
| 14 | -168750405673899000 |
| 15 | 3719099270015849040 |
| 16 | -82288133754592611642 |
| 17 | 1828585054153956768612 |
| 18 | -40828782977534929747524 |
| 19 | 915461326204911371035320 |