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 | 1 |
| 3 | -1 |
| 4 | 1 |
| 5 | 2 |
| 6 | 1 |
| 7 | -3 |
| 8 | -6 |
| 9 | 1 |
| 10 | 24 |
| 11 | 1 |
| 12 | -10 |
| 13 | 30 |
| 14 | -120 |
| 15 | 1 |
| 16 | 720 |
| 17 | 1 |
| 18 | -35 |
| 19 | -630 |
| 20 | -5040 |
| 21 | 1 |
| 22 | 560 |
| 23 | 40320 |
| 24 | 1 |
| 25 | -126 |
| 26 | 22680 |
| 27 | -362880 |
| 28 | 1 |
| 29 | 3628800 |
| 30 | 1 |
| 31 | -462 |
| 32 | 11550 |
| 33 | -92400 |
| 34 | -1247400 |
| 35 | -39916800 |
| 36 | 1 |
| 37 | 479001600 |
| 38 | 1 |
| 39 | -1716 |
| 40 | 97297200 |
| 41 | -6227020800 |