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 | -48 |
| 2 | 1080 |
| 3 | -15040 |
| 4 | 143820 |
| 5 | -985824 |
| 6 | 4857920 |
| 7 | -16295040 |
| 8 | 28412910 |
| 9 | 38671600 |
| 10 | -424520544 |
| 11 | 1268350272 |
| 12 | -1211937160 |
| 13 | -4306546080 |
| 14 | 18293091840 |
| 15 | -23522231424 |
| 16 | -26299018683 |
| 17 | 137218594320 |
| 18 | -150999182320 |
| 19 | -134713340160 |