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 | 1 |
| 2 | 2 |
| 3 | -2 |
| 4 | 1 |
| 5 | 40 |
| 6 | -40 |
| 7 | 20 |
| 8 | -6 |
| 9 | 1 |
| 10 | 2240 |
| 11 | -2240 |
| 12 | 1120 |
| 13 | -360 |
| 14 | 80 |
| 15 | -12 |
| 16 | 1 |
| 17 | 246400 |
| 18 | -246400 |
| 19 | 123200 |
| 20 | -40320 |
| 21 | 9520 |
| 22 | -1680 |
| 23 | 220 |
| 24 | -20 |
| 25 | 1 |
| 26 | 44844800 |
| 27 | -44844800 |
| 28 | 22422400 |
| 29 | -7392000 |
| 30 | 1786400 |
| 31 | -332640 |
| 32 | 48720 |
| 33 | -5600 |
| 34 | 490 |
| 35 | -30 |
| 36 | 1 |
| 37 | 12197785600 |
| 38 | -12197785600 |
| 39 | 6098892800 |
| 40 | -2018016000 |
| 41 | 493292800 |