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 | 0 |
| 2 | -2 |
| 3 | -2 |
| 4 | 0 |
| 5 | 6 |
| 6 | 0 |
| 7 | 24 |
| 8 | 0 |
| 9 | -24 |
| 10 | 24 |
| 11 | 0 |
| 12 | -240 |
| 13 | 0 |
| 14 | 120 |
| 15 | 0 |
| 16 | -720 |
| 17 | 0 |
| 18 | 2400 |
| 19 | 0 |
| 20 | -720 |
| 21 | -720 |
| 22 | 0 |
| 23 | 15120 |
| 24 | 0 |
| 25 | -25200 |
| 26 | 0 |
| 27 | 5040 |
| 28 | 0 |
| 29 | 40320 |
| 30 | 0 |
| 31 | -282240 |
| 32 | 0 |
| 33 | 282240 |
| 34 | 0 |
| 35 | -40320 |
| 36 | 40320 |
| 37 | 0 |
| 38 | -1451520 |
| 39 | 0 |
| 40 | 5080320 |
| 41 | 0 |
| 42 | -3386880 |
| 43 | 0 |
| 44 | 362880 |
| 45 | 0 |
| 46 | -3628800 |
| 47 | 0 |
| 48 | 43545600 |
| 49 | 0 |
| 50 | -91445760 |
| 51 | 0 |
| 52 | 43545600 |
| 53 | 0 |
| 54 | -3628800 |