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 | 2 |
| 2 | -1 |
| 3 | 6 |
| 4 | -6 |
| 5 | 1 |
| 6 | 24 |
| 7 | -36 |
| 8 | 12 |
| 9 | -1 |
| 10 | 120 |
| 11 | -240 |
| 12 | 120 |
| 13 | -20 |
| 14 | 1 |
| 15 | 720 |
| 16 | -1800 |
| 17 | 1200 |
| 18 | -300 |
| 19 | 30 |
| 20 | -1 |
| 21 | 5040 |
| 22 | -15120 |
| 23 | 12600 |
| 24 | -4200 |
| 25 | 630 |
| 26 | -42 |
| 27 | 1 |
| 28 | 40320 |
| 29 | -141120 |
| 30 | 141120 |
| 31 | -58800 |
| 32 | 11760 |
| 33 | -1176 |
| 34 | 56 |
| 35 | -1 |
| 36 | 362880 |
| 37 | -1451520 |
| 38 | 1693440 |
| 39 | -846720 |
| 40 | 211680 |
| 41 | -28224 |
| 42 | 2016 |