nextpow2357(n,inc)

Find next power of 2,3,5,7,... for optimal FFT sizing

The FFT is optimal if the number of samples is 2^N × 3^O × 5^P ..... The function accepts a number and returns the exact power of 2,3,5,7,9,11 greater or smaller than the number. It is a generalization of nextpow2