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 | 27 |
| 5 | -76 |
| 6 | 95 |
| 7 | -295 |
| 8 | 2035 |
| 9 | -8119 |
| 10 | 22714 |
| 11 | -66793 |
| 12 | 254223 |
| 13 | -988651 |
| 14 | 3444055 |
| 15 | -11402626 |
| 16 | 39248691 |
| 17 | -141740051 |
| 18 | 511583207 |
| 19 | -1798826901 |
| 20 | 6256648862 |
| 21 | -22054706773 |
| 22 | 78889160635 |
| 23 | -281698897727 |
| 24 | 996551999479 |
| 25 | -3520566280801 |
| 26 | 12522382445455 |
| 27 | -44731559517301 |