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 | 5 |
| 4 | 0 |
| 5 | 44 |
| 6 | -245 |
| 7 | 1917 |
| 8 | -17976 |
| 9 | 191760 |
| 10 | -2268017 |
| 11 | 29862645 |
| 12 | -432485152 |
| 13 | 6819543964 |
| 14 | -116400819509 |
| 15 | 2138673633397 |
| 16 | -42078450265744 |
| 17 | 882702459984256 |
| 18 | -19667723002057473 |
| 19 | 463866294631620941 |
| 20 | -11545312970532620104 |
| 21 | 302416006623761207804 |
| 22 | -8316019118849688156693 |