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 | -4 |
| 2 | 9 |
| 3 | -24 |
| 4 | 69 |
| 5 | -204 |
| 6 | 609 |
| 7 | -1824 |
| 8 | 5469 |
| 9 | -16404 |
| 10 | 49209 |
| 11 | -147624 |
| 12 | 442869 |
| 13 | -1328604 |
| 14 | 3985809 |
| 15 | -11957424 |
| 16 | 35872269 |
| 17 | -107616804 |
| 18 | 322850409 |
| 19 | -968551224 |
| 20 | 2905653669 |
| 21 | -8716961004 |
| 22 | 26150883009 |
| 23 | -78452649024 |
| 24 | 235357947069 |
| 25 | -706073841204 |
| 26 | 2118221523609 |