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) |
|---|---|
| 1 | 0 |
| 2 | -9 |
| 3 | 240 |
| 4 | -6300 |
| 5 | 181440 |
| 6 | -5821200 |
| 7 | 207567360 |
| 8 | -8172964800 |
| 9 | 352864512000 |
| 10 | -16593453676800 |
| 11 | 844757641728000 |
| 12 | -46306798060723200 |
| 13 | 2720119606364160000 |
| 14 | -170493211041753600000 |
| 15 | 11359219476176732160000 |
| 16 | -801737767492652390400000 |
| 17 | 59762476409805241712640000 |
| 18 | -4691769415367001788620800000 |