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 | -10 |
| 2 | 30 |
| 3 | -20 |
| 4 | -10 |
| 5 | -12 |
| 6 | -20 |
| 7 | -40 |
| 8 | -90 |
| 9 | -220 |
| 10 | -572 |
| 11 | -1560 |
| 12 | -4420 |
| 13 | -12920 |
| 14 | -38760 |
| 15 | -118864 |
| 16 | -371450 |
| 17 | -1179900 |
| 18 | -3801900 |
| 19 | -12406200 |
| 20 | -40940460 |
| 21 | -136468200 |
| 22 | -459029400 |
| 23 | -1556708400 |
| 24 | -5318753700 |
| 25 | -18296512728 |
| 26 | -63334082520 |