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 | -1 |
| 3 | 1 |
| 4 | 13 |
| 5 | -5 |
| 6 | -121 |
| 7 | 49 |
| 8 | 1093 |
| 9 | -809 |
| 10 | -49205 |
| 11 | 20317 |
| 12 | 61203943 |
| 13 | -722813 |
| 14 | -5580127 |
| 15 | 34607305 |
| 16 | 25949996501 |
| 17 | -2145998417 |
| 18 | -2832495743227 |
| 19 | 167317266613 |
| 20 | 101471818419863 |
| 21 | -16020403322021 |
| 22 | -4469253897850313 |
| 23 | 1848020950359841 |
| 24 | 11126033443528968583 |
| 25 | -252778977216700025 |