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 | -1 |
| 2 | 3 |
| 3 | -1 |
| 4 | 10 |
| 5 | -15 |
| 6 | -1 |
| 7 | 15 |
| 8 | 10 |
| 9 | -105 |
| 10 | 105 |
| 11 | -1 |
| 12 | 21 |
| 13 | 35 |
| 14 | -210 |
| 15 | -280 |
| 16 | 1260 |
| 17 | -945 |
| 18 | -1 |
| 19 | 28 |
| 20 | 56 |
| 21 | 35 |
| 22 | -378 |
| 23 | -1260 |
| 24 | -280 |
| 25 | 3150 |
| 26 | 6300 |
| 27 | -17325 |
| 28 | 10395 |
| 29 | -1 |
| 30 | 36 |
| 31 | 84 |
| 32 | 126 |
| 33 | -630 |
| 34 | -2520 |
| 35 | -1575 |
| 36 | -2100 |
| 37 | 6930 |
| 38 | 34650 |
| 39 | 15400 |
| 40 | -51975 |
| 41 | -138600 |
| 42 | 270270 |
| 43 | -135135 |
| 44 | -1 |
| 45 | 45 |
| 46 | 120 |
| 47 | 210 |
| 48 | 126 |
| 49 | -990 |
| 50 | -4620 |
| 51 | -6930 |
| 52 | -4620 |
| 53 | -5775 |