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) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | -1 |
| 4 | -3 |
| 5 | 0 |
| 6 | 12 |
| 7 | 12 |
| 8 | -36 |
| 9 | -96 |
| 10 | 120 |
| 11 | 792 |
| 12 | -48 |
| 13 | -6384 |
| 14 | -6000 |
| 15 | 45072 |
| 16 | 93072 |
| 17 | -312576 |
| 18 | -1243296 |
| 19 | 2195040 |
| 20 | 17114592 |
| 21 | -9225888 |
| 22 | -231715584 |
| 23 | -102553152 |
| 24 | 3141465024 |
| 25 | 4679762304 |
| 26 | -42442213056 |
| 27 | -112638647616 |
| 28 | 566436761280 |
| 29 | 2368655123136 |
| 30 | -6694333057344 |
| 31 | -44592815027520 |