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 | -5 |
| 2 | 20 |
| 3 | -85 |
| 4 | 350 |
| 5 | -1470 |
| 6 | 6090 |
| 7 | -25485 |
| 8 | 105830 |
| 9 | -442150 |
| 10 | 1838240 |
| 11 | -7673330 |
| 12 | 31923220 |
| 13 | -133186760 |
| 14 | 554325750 |
| 15 | -2311919325 |
| 16 | 9624918150 |
| 17 | -40133290350 |
| 18 | 167114005800 |
| 19 | -696706389750 |
| 20 | 2901470571300 |
| 21 | -12094930814100 |
| 22 | 50375156502900 |
| 23 | -209972720898450 |
| 24 | 874600454065500 |