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 | 4 |
| 3 | -11 |
| 4 | 28 |
| 5 | -72 |
| 6 | 188 |
| 7 | -493 |
| 8 | 1292 |
| 9 | -3383 |
| 10 | 8856 |
| 11 | -23184 |
| 12 | 60696 |
| 13 | -158905 |
| 14 | 416020 |
| 15 | -1089155 |
| 16 | 2851444 |
| 17 | -7465176 |
| 18 | 19544084 |
| 19 | -51167077 |
| 20 | 133957148 |
| 21 | -350704367 |
| 22 | 918155952 |
| 23 | -2403763488 |
| 24 | 6293134512 |
| 25 | -16475640049 |
| 26 | 43133785636 |
| 27 | -112925716859 |
| 28 | 295643364940 |
| 29 | -774004377960 |