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 | 60 |
| 3 | -504 |
| 4 | 2160 |
| 5 | -3168 |
| 6 | 786240 |
| 7 | -51840 |
| 8 | 1762560 |
| 9 | -82736640 |
| 10 | 1437004800 |
| 11 | -858470400 |
| 12 | 101896704000 |
| 13 | -1881169920 |
| 14 | 8659353600 |
| 15 | -855305256960 |
| 16 | 14071151001600 |
| 17 | -150493593600 |
| 18 | 8252165711462400 |
| 19 | -70431001804800 |
| 20 | 24434139856896000 |
| 21 | -1076294062964736000 |