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 | -1 |
| 6 | 6 |
| 7 | -2 |
| 8 | -1 |
| 9 | -3 |
| 10 | 24 |
| 11 | -6 |
| 12 | -2 |
| 13 | -3 |
| 14 | -13 |
| 15 | 120 |
| 16 | -24 |
| 17 | -6 |
| 18 | -6 |
| 19 | -13 |
| 20 | -71 |
| 21 | 720 |
| 22 | -120 |
| 23 | -24 |
| 24 | -18 |
| 25 | -26 |
| 26 | -71 |
| 27 | -461 |
| 28 | 5040 |
| 29 | -720 |
| 30 | -120 |
| 31 | -72 |
| 32 | -78 |
| 33 | -142 |
| 34 | -461 |
| 35 | -3447 |
| 36 | 40320 |
| 37 | -5040 |
| 38 | -720 |
| 39 | -360 |
| 40 | -312 |
| 41 | -426 |
| 42 | -922 |
| 43 | -3447 |
| 44 | -29093 |
| 45 | 362880 |
| 46 | -40320 |
| 47 | -5040 |
| 48 | -2160 |
| 49 | -1560 |