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 | 0 |
| 3 | 1 |
| 4 | -3 |
| 5 | 7 |
| 6 | -15 |
| 7 | 30 |
| 8 | -55 |
| 9 | 90 |
| 10 | -125 |
| 11 | 125 |
| 12 | 0 |
| 13 | -450 |
| 14 | 1625 |
| 15 | -4250 |
| 16 | 9500 |
| 17 | -18999 |
| 18 | 34357 |
| 19 | -55454 |
| 20 | 75735 |
| 21 | -70890 |
| 22 | -26333 |
| 23 | 379049 |
| 24 | -1352078 |
| 25 | 3713650 |
| 26 | -9000225 |
| 27 | 20136806 |
| 28 | -42409968 |
| 29 | 84819937 |
| 30 | -161567265 |
| 31 | 292710630 |
| 32 | -501416815 |
| 33 | 801992970 |
| 34 | -1167081365 |
| 35 | 1453179125 |