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 | -2 |
| 3 | 5 |
| 4 | -15 |
| 5 | 52 |
| 6 | -200 |
| 7 | 825 |
| 8 | -3565 |
| 9 | 15900 |
| 10 | -72532 |
| 11 | 336539 |
| 12 | -1582593 |
| 13 | 7524705 |
| 14 | -36111810 |
| 15 | 174695712 |
| 16 | -851020367 |
| 17 | 4171156249 |
| 18 | -20555470155 |
| 19 | 101787990805 |
| 20 | -506227992092 |
| 21 | 2527493643612 |
| 22 | -12663916942984 |
| 23 | 63656297034920 |
| 24 | -320914409885850 |
| 25 | 1622205233276889 |