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 | -3 |
| 2 | 3 |
| 3 | 9 |
| 4 | 3 |
| 5 | -63 |
| 6 | -357 |
| 7 | -1431 |
| 8 | -5037 |
| 9 | -16623 |
| 10 | -52917 |
| 11 | -164871 |
| 12 | -506877 |
| 13 | -1545183 |
| 14 | -4684677 |
| 15 | -14152311 |
| 16 | -42653517 |
| 17 | -128353743 |
| 18 | -385847637 |
| 19 | -1159115751 |
| 20 | -3480492957 |
| 21 | -10447770303 |
| 22 | -31355893797 |
| 23 | -94092847191 |
| 24 | -282328873197 |
| 25 | -847087282863 |
| 26 | -2541463175157 |