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 | 1 |
| 4 | -4 |
| 5 | 2 |
| 6 | -1 |
| 7 | 9 |
| 8 | -18 |
| 9 | 6 |
| 10 | 1 |
| 11 | -16 |
| 12 | 72 |
| 13 | -96 |
| 14 | 24 |
| 15 | -1 |
| 16 | 25 |
| 17 | -200 |
| 18 | 600 |
| 19 | -600 |
| 20 | 120 |
| 21 | 1 |
| 22 | -36 |
| 23 | 450 |
| 24 | -2400 |
| 25 | 5400 |
| 26 | -4320 |
| 27 | 720 |
| 28 | -1 |
| 29 | 49 |
| 30 | -882 |
| 31 | 7350 |
| 32 | -29400 |
| 33 | 52920 |
| 34 | -35280 |
| 35 | 5040 |
| 36 | 1 |
| 37 | -64 |
| 38 | 1568 |
| 39 | -18816 |
| 40 | 117600 |
| 41 | -376320 |
| 42 | 564480 |
| 43 | -322560 |
| 44 | 40320 |
| 45 | -1 |
| 46 | 81 |
| 47 | -2592 |
| 48 | 42336 |
| 49 | -381024 |
| 50 | 1905120 |
| 51 | -5080320 |
| 52 | 6531840 |
| 53 | -3265920 |
| 54 | 362880 |