The odd numbered terms go 2, 3, 4, 5, 6, 7, ...  add 1 each time

The even numbered terms go 7, 26, 45, 64, 83, 102, ... add 19 each time.

So the next term after 4 is 45.

[It could also be 7+26 which is 33, instead of 45.]
There are thousands of other possible answers, too,
but these are as good as any, and they're simple.  I 
cannot understand why schools are teaching such problems 
as this, as if there were only one answer, when there 
are many.

Edwin