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 | 0 |
| 2 | 1 |
| 3 | -3 |
| 4 | 16 |
| 5 | -100 |
| 6 | 760 |
| 7 | -6720 |
| 8 | 67940 |
| 9 | -772560 |
| 10 | 9760100 |
| 11 | -135617900 |
| 12 | 2055532400 |
| 13 | -33748556400 |
| 14 | 596675513200 |
| 15 | -11302050942000 |
| 16 | 228340292986000 |
| 17 | -4901379615184000 |
| 18 | 111394219174810000 |
| 19 | -2672242230261006000 |