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 | 1 |
| 5 | -119 |
| 6 | -719 |
| 7 | -2519 |
| 8 | -6719 |
| 9 | 166321 |
| 10 | 3598561 |
| 11 | 29882161 |
| 12 | 159572161 |
| 13 | -389343239 |
| 14 | -55939643759 |
| 15 | -974399385959 |
| 16 | -9282412863359 |
| 17 | -46891283580959 |
| 18 | 1814094098389441 |
| 19 | 67045782535457761 |
| 20 | 1076141148146824321 |
| 21 | 61735522719009663721 |
| 22 | 1058382395842664859121 |