Find the sum of the first 15 terms of the series 4+16+64+256+

A sum of an geometric sequence is a(1-r^n)/(1-r) where n=15 in this problem and r=4 since each term is being multiplied by 4 to get the next term. a also equals 4 since that is the first number. So now you have 4(1-4^15)/(1-4) which you can type into your calculator. Be sure to use the parenthesis so the calculator will know what is in the numerator and what is in the denominator,

Do you mean conversion factor?