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 | -2 |
| 3 | 5 |
| 4 | -18 |
| 5 | 70 |
| 6 | -282 |
| 7 | 1179 |
| 8 | -5104 |
| 9 | 22634 |
| 10 | -102128 |
| 11 | 467637 |
| 12 | -2168208 |
| 13 | 10157664 |
| 14 | -48005858 |
| 15 | 228607728 |
| 16 | -1095885048 |
| 17 | 5284044080 |
| 18 | -25609804110 |
| 19 | 124693451466 |
| 20 | -609641464746 |
| 21 | 2991742731876 |
| 22 | -14731354000792 |
| 23 | 72761153346680 |
| 24 | -360397156557696 |
| 25 | 1789733084330806 |
| 26 | -8909067981051118 |