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 | 2 |
| 3 | 2 |
| 4 | 0 |
| 5 | 0 |
| 6 | -2 |
| 7 | 2 |
| 8 | -2 |
| 9 | 6 |
| 10 | -10 |
| 11 | 14 |
| 12 | -28 |
| 13 | 52 |
| 14 | -86 |
| 15 | 158 |
| 16 | -296 |
| 17 | 528 |
| 18 | -966 |
| 19 | 1806 |
| 20 | -3328 |
| 21 | 6160 |
| 22 | -11542 |
| 23 | 21590 |
| 24 | -40418 |
| 25 | 76118 |
| 26 | -143598 |
| 27 | 271138 |
| 28 | -513524 |
| 29 | 974620 |
| 30 | -1851962 |
| 31 | 3525682 |
| 32 | -6723794 |
| 33 | 12839190 |
| 34 | -24550602 |
| 35 | 47010286 |
| 36 | -90122848 |
| 37 | 172970032 |
| 38 | -332352998 |
| 39 | 639260230 |