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 | 2 |
| 2 | -1 |
| 3 | 3 |
| 4 | -10 |
| 5 | 36 |
| 6 | -137 |
| 7 | 543 |
| 8 | -2219 |
| 9 | 9285 |
| 10 | -39587 |
| 11 | 171369 |
| 12 | -751236 |
| 13 | 3328218 |
| 14 | -14878455 |
| 15 | 67030785 |
| 16 | -304036170 |
| 17 | 1387247580 |
| 18 | -6363044315 |
| 19 | 29323149825 |
| 20 | -135700543190 |
| 21 | 630375241380 |
| 22 | -2938391049395 |
| 23 | 13739779184085 |
| 24 | -64430797069375 |
| 25 | 302934667061301 |
| 26 | -1427763630578197 |