Question 986820
1+4 +16 + 64+....

number of terms = 16

first term = 1

we get the next term by multiplying by a factor of 4

so 4 is called the common rato of the consecutive terms

hence this is a geometric sequence

the formula for sum of n terms of a geometric sequence is 


Use this formula:

{{{Sn = a*(1-r^n)/(1-r)}}}

a is the first term 
r is the "common ratio" between terms 
n is the number of terms 

Sum of  16 terms={{{1(1-4^16)/(1-4)}}}


=1431655765