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 | -40 |
| 2 | 740 |
| 3 | -8320 |
| 4 | 62530 |
| 5 | -322048 |
| 6 | 1085240 |
| 7 | -1799680 |
| 8 | -2821065 |
| 9 | 26012480 |
| 10 | -66837420 |
| 11 | 35093760 |
| 12 | 268749870 |
| 13 | -783902720 |
| 14 | 526221400 |
| 15 | 1691816960 |
| 16 | -3960854625 |
| 17 | 1042577120 |
| 18 | 5103133240 |
| 19 | -380798080 |
| 20 | -10159511430 |