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 | 0 |
| 3 | -2 |
| 4 | -6 |
| 5 | -17 |
| 6 | -46 |
| 7 | -132 |
| 8 | -402 |
| 9 | -1314 |
| 10 | -4613 |
| 11 | -17313 |
| 12 | -68893 |
| 13 | -288556 |
| 14 | -1269637 |
| 15 | -5907157 |
| 16 | -29489299 |
| 17 | -160431708 |
| 18 | -955478664 |
| 19 | -6145884133 |
| 20 | -41584238971 |
| 21 | -287650358748 |
| 22 | -1984825313901 |
| 23 | -13377544470631 |
| 24 | -86142095523089 |
| 25 | -512881404732949 |
| 26 | -2634567148684612 |
| 27 | -9205461936290915 |
| 28 | 17544751152746927 |