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 | -1 |
| 3 | 2 |
| 4 | -1 |
| 5 | 6 |
| 6 | -6 |
| 7 | -1 |
| 8 | 8 |
| 9 | 6 |
| 10 | -36 |
| 11 | 24 |
| 12 | -1 |
| 13 | 10 |
| 14 | 20 |
| 15 | -60 |
| 16 | -90 |
| 17 | 240 |
| 18 | -120 |
| 19 | -1 |
| 20 | 12 |
| 21 | 30 |
| 22 | -90 |
| 23 | 20 |
| 24 | -360 |
| 25 | 480 |
| 26 | -90 |
| 27 | 1080 |
| 28 | -1800 |
| 29 | 720 |
| 30 | -1 |
| 31 | 14 |
| 32 | 42 |
| 33 | -126 |
| 34 | 70 |
| 35 | -630 |
| 36 | 840 |
| 37 | -420 |
| 38 | -630 |
| 39 | 5040 |
| 40 | -4200 |
| 41 | 2520 |
| 42 | -12600 |
| 43 | 15120 |
| 44 | -5040 |
| 45 | -1 |
| 46 | 16 |
| 47 | 56 |
| 48 | -168 |
| 49 | 112 |
| 50 | -1008 |
| 51 | 1344 |
| 52 | 70 |