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 | 0 |
| 2 | 1 |
| 3 | -1 |
| 4 | 1 |
| 5 | -1 |
| 6 | 0 |
| 7 | 5 |
| 8 | -20 |
| 9 | 55 |
| 10 | -125 |
| 11 | 250 |
| 12 | -450 |
| 13 | 725 |
| 14 | -1000 |
| 15 | 1000 |
| 16 | 1 |
| 17 | -3642 |
| 18 | 13278 |
| 19 | -35344 |
| 20 | 81720 |
| 21 | -174098 |
| 22 | 352716 |
| 23 | -694904 |
| 24 | 1355322 |
| 25 | -2652200 |
| 26 | 5245956 |
| 27 | -10491911 |
| 28 | 21097440 |
| 29 | -42262518 |
| 30 | 83482620 |
| 31 | -161013975 |
| 32 | 300338820 |
| 33 | -536165400 |
| 34 | 903201960 |
| 35 | -1401448500 |