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 | 0 |
| 1 | 6 |
| 2 | -15 |
| 3 | 45 |
| 4 | -129 |
| 5 | 372 |
| 6 | -1071 |
| 7 | 3084 |
| 8 | -8880 |
| 9 | 25569 |
| 10 | -73623 |
| 11 | 211989 |
| 12 | -610398 |
| 13 | 1757571 |
| 14 | -5060724 |
| 15 | 14571774 |
| 16 | -41957751 |
| 17 | 120812529 |
| 18 | -347865813 |
| 19 | 1001639688 |
| 20 | -2884106535 |
| 21 | 8304453792 |
| 22 | -23911721688 |
| 23 | 68851058529 |
| 24 | -198248721795 |
| 25 | 570834443697 |
| 26 | -1643652272562 |