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 | 1 |
| 2 | 0 |
| 3 | -1 |
| 4 | -4 |
| 5 | -5 |
| 6 | -20 |
| 7 | 9 |
| 8 | -208 |
| 9 | 855 |
| 10 | -6180 |
| 11 | 41549 |
| 12 | -321792 |
| 13 | 2651155 |
| 14 | -23664420 |
| 15 | 225865769 |
| 16 | -2301032256 |
| 17 | 24901626095 |
| 18 | -285356879940 |
| 19 | 3451591584869 |
| 20 | -43947119045600 |
| 21 | 587529302036875 |
| 22 | -8228722825167940 |
| 23 | 120487046847246049 |
| 24 | -1840906518665985824 |