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 | 3 |
| 2 | -1 |
| 3 | 15 |
| 4 | -10 |
| 5 | 1 |
| 6 | 105 |
| 7 | -105 |
| 8 | 21 |
| 9 | -1 |
| 10 | 945 |
| 11 | -1260 |
| 12 | 378 |
| 13 | -36 |
| 14 | 1 |
| 15 | 10395 |
| 16 | -17325 |
| 17 | 6930 |
| 18 | -990 |
| 19 | 55 |
| 20 | -1 |
| 21 | 135135 |
| 22 | -270270 |
| 23 | 135135 |
| 24 | -25740 |
| 25 | 2145 |
| 26 | -78 |
| 27 | 1 |
| 28 | 2027025 |
| 29 | -4729725 |
| 30 | 2837835 |
| 31 | -675675 |
| 32 | 75075 |
| 33 | -4095 |
| 34 | 105 |
| 35 | -1 |
| 36 | 34459425 |
| 37 | -91891800 |
| 38 | 64324260 |
| 39 | -18378360 |
| 40 | 2552550 |
| 41 | -185640 |
| 42 | 7140 |
| 43 | -136 |