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 | -56 |
| 2 | 1512 |
| 3 | -26208 |
| 4 | 327656 |
| 5 | -3147984 |
| 6 | 24189984 |
| 7 | -152867520 |
| 8 | 811401192 |
| 9 | -3681079640 |
| 10 | 14500933104 |
| 11 | -50376047904 |
| 12 | 156797510688 |
| 13 | -444306558864 |
| 14 | 1163495873088 |
| 15 | -2851049839680 |
| 16 | 6597606440936 |
| 17 | -14512424533488 |
| 18 | 30505974273096 |
| 19 | -61591664700384 |
| 20 | 119983597365744 |
| 21 | -226303038736128 |