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 | -1 |
| 3 | 9 |
| 4 | -20 |
| 5 | 62 |
| 6 | -174 |
| 7 | 556 |
| 8 | -1660 |
| 9 | 4911 |
| 10 | -14693 |
| 11 | 44357 |
| 12 | -133053 |
| 13 | 398389 |
| 14 | -1195207 |
| 15 | 3587853 |
| 16 | -10763270 |
| 17 | 32283452 |
| 18 | -96850386 |
| 19 | 290570104 |
| 20 | -871710994 |
| 21 | 2615074146 |
| 22 | -7845220010 |
| 23 | 23535839600 |
| 24 | -70607518824 |
| 25 | 211822017739 |
| 26 | -635466060265 |
| 27 | 1906399774635 |
| 28 | -5719199303975 |