Take the log using base 2. If the answer is an integer than your number is in the sequence
if i have a number i want to know if it is in the sequence or not
but i don't want the way which i will divide the number by 2 till i found it 2 or not i want a function from one or two steps to know if this number is from sequence or not
That's very strange! You say that you do not know what a logarithm is but you think it will be easier to take the logarithm?
If you really do not know about logarithms (especially taking the logarithm, base 2) I would recommend repeatedly dividing by 2. If you eventually arrive at 1 without any fractions, the number is a power of 2.