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 | -7 |
| 2 | 42 |
| 3 | -259 |
| 4 | 1582 |
| 5 | -9702 |
| 6 | 59388 |
| 7 | -363867 |
| 8 | 2228310 |
| 9 | -13649650 |
| 10 | 83599852 |
| 11 | -512063790 |
| 12 | 3136339276 |
| 13 | -19210260076 |
| 14 | 117662192928 |
| 15 | -720683271819 |
| 16 | 4414176556902 |
| 17 | -27036862348986 |
| 18 | 165600668448348 |
| 19 | -1014304512179994 |
| 20 | 6212613590747172 |
| 21 | -38052263986931796 |