Sequence for Isomers of Alkanes

[Hyperreality]

Today in my chemistry glass, my teacher was talking about isomers in organic chemistry.

I was wondering if there is a formula or a way to predict the number of isomers each alkanes compound has.

[NSX]

If I remember correctly, the alkanes are:

C(n) H(n+2)

n & n+2 are supposed to be subscipted
[:)]

[FZ+]

From http://www.faculty.sfasu.edu/chengs/teaching/chapter4.htm

Constitutional isomers are possible for alkanes with four or more carbons. There is no simple expression to calculate the number of isomers.