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