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 | -2 |
| 2 | 3 |
| 3 | -2 |
| 4 | -6 |
| 5 | 28 |
| 6 | -61 |
| 7 | 54 |
| 8 | 158 |
| 9 | -860 |
| 10 | 2062 |
| 11 | -2004 |
| 12 | -5804 |
| 13 | 33720 |
| 14 | -84509 |
| 15 | 86054 |
| 16 | 247862 |
| 17 | -1492908 |
| 18 | 3838298 |
| 19 | -4019452 |
| 20 | -11537556 |
| 21 | 71101832 |
| 22 | -185868978 |
| 23 | 198310460 |
| 24 | 567902572 |
| 25 | -3555617432 |
| 26 | 9404104764 |
| 27 | -10168382696 |
| 28 | -29069700056 |
| 29 | 184127171952 |
| 30 | -491229517661 |