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 | 0 |
| 1 | 1 |
| 2 | 1 |
| 3 | -1 |
| 4 | -1 |
| 5 | 5 |
| 6 | 5 |
| 7 | -15 |
| 8 | -15 |
| 9 | 55 |
| 10 | 55 |
| 11 | -197 |
| 12 | -197 |
| 13 | 727 |
| 14 | 727 |
| 15 | -2705 |
| 16 | -2705 |
| 17 | 10165 |
| 18 | 10165 |
| 19 | -38455 |
| 20 | -38455 |
| 21 | 146301 |
| 22 | 146301 |
| 23 | -559131 |
| 24 | -559131 |
| 25 | 2145025 |
| 26 | 2145025 |
| 27 | -8255575 |
| 28 | -8255575 |
| 29 | 31861025 |
| 30 | 31861025 |
| 31 | -123256495 |
| 32 | -123256495 |
| 33 | 477823895 |
| 34 | 477823895 |
| 35 | -1855782325 |
| 36 | -1855782325 |
| 37 | 7219352975 |