Negatives Come in Blocks

Difficulty: Hard · Topics: Discrete Mathematics, Sets, Subsets

The set B, at least one element of which is negative, is a five-element subset of

A=\-3,-2,-1,0,1,2,3,4,5\.

For every negative number in B, the number one greater than it is an element of B as well.

How many different sets B can be written?