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 | 5 |
| 5 | -10 |
| 6 | 15 |
| 7 | -15 |
| 8 | 0 |
| 9 | 50 |
| 10 | -175 |
| 11 | 450 |
| 12 | -1000 |
| 13 | 2000 |
| 14 | -3625 |
| 15 | 5875 |
| 16 | -8125 |
| 17 | 8125 |
| 18 | 0 |
| 19 | -29375 |
| 20 | 106250 |
| 21 | -278125 |
| 22 | 621875 |
| 23 | -1243750 |
| 24 | 2250000 |
| 25 | -3640625 |
| 26 | 5031250 |
| 27 | -5031250 |
| 28 | 0 |
| 29 | 18203125 |
| 30 | -65859375 |
| 31 | 172421875 |
| 32 | -385546875 |
| 33 | 771093750 |
| 34 | -1394921875 |
| 35 | 2257031250 |
| 36 | -3119140625 |
| 37 | 3119140625 |
| 38 | 0 |