The standard resistor/capacitor/inductance values are build the same way

as music notes frequencies. For example the E12 series has 12 different

values between each decade, the factor between successive values is

calculated like this :

k = 10^(1/12) = 1.2115

V1 = 10 and Vn = k*V(n-1)

Which gives the following values (rounded)

calculated values: 10, 12, 15, 18, 22, 26, 32, 38, 46, 56, 68, 83, 100

E12 values : 10, 12, 15, 18, 22, 27, 33, 38, 47, 56, 68, 83, 100