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 | 1 |
| 2 | -7 |
| 3 | 25 |
| 4 | -79 |
| 5 | 241 |
| 6 | -727 |
| 7 | 2185 |
| 8 | -6559 |
| 9 | 19681 |
| 10 | -59047 |
| 11 | 177145 |
| 12 | -531439 |
| 13 | 1594321 |
| 14 | -4782967 |
| 15 | 14348905 |
| 16 | -43046719 |
| 17 | 129140161 |
| 18 | -387420487 |
| 19 | 1162261465 |
| 20 | -3486784399 |
| 21 | 10460353201 |
| 22 | -31381059607 |
| 23 | 94143178825 |
| 24 | -282429536479 |