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 | -1 |
| 3 | 2 |
| 4 | -5 |
| 5 | 12 |
| 6 | -30 |
| 7 | 82 |
| 8 | -233 |
| 9 | 668 |
| 10 | -1949 |
| 11 | 5802 |
| 12 | -17503 |
| 13 | 53302 |
| 14 | -163783 |
| 15 | 507418 |
| 16 | -1582869 |
| 17 | 4966790 |
| 18 | -15667573 |
| 19 | 49658264 |
| 20 | -158059506 |
| 21 | 505013014 |
| 22 | -1619144976 |
| 23 | 5207596574 |
| 24 | -16797286048 |
| 25 | 54323516786 |
| 26 | -176113786590 |
| 27 | 572236347200 |
| 28 | -1863213388504 |
| 29 | 6078422747600 |
| 30 | -19865661574555 |