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 | -28 |
| 2 | 420 |
| 3 | -4480 |
| 4 | 38052 |
| 5 | -273336 |
| 6 | 1723008 |
| 7 | -9770240 |
| 8 | 50722980 |
| 9 | -244273820 |
| 10 | 1102294984 |
| 11 | -4698110592 |
| 12 | 19034512000 |
| 13 | -73696070840 |
| 14 | 273868321536 |
| 15 | -980502270720 |
| 16 | 3392689809572 |
| 17 | -11376760267320 |
| 18 | 37060195850020 |