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) |
|---|---|
| 1 | 1 |
| 2 | -4 |
| 3 | 26 |
| 4 | -208 |
| 5 | 1859 |
| 6 | -17790 |
| 7 | 178308 |
| 8 | -1847882 |
| 9 | 19640154 |
| 10 | -212911066 |
| 11 | 2345049018 |
| 12 | -26168243862 |
| 13 | 295214515662 |
| 14 | -3361428239216 |
| 15 | 38580429168968 |
| 16 | -445874925644701 |
| 17 | 5184317812361117 |
| 18 | -60603410700370525 |
| 19 | 711826341810784570 |
| 20 | -8396670336877539127 |
| 21 | 99428914632341468974 |