Tuesday, June 21, 2016

Project Euler 401 Sum of squares of divisors

The divisors of 6 are 1,2,3 and 6.
The sum of the squares of these numbers is 1+4+9+36=50.
Let sigma2(n) represent the sum of the squares of the divisors of n. Thus sigma2(6)=50.
Let SIGMA2 represent the summatory function of sigma2, that is SIGMA2(n)=∑sigma2(i) for i=1 to n.
The first 6 values of SIGMA2 are: 1,6,16,37,63 and 113.
Find SIGMA2(1015) modulo 109.

I have to found SIGMA2(10^15)
for bruteforce I cant't solve in my life time

1^2 + 2^2 + 3^2 + 4^2+ 5^2 + .... N^2 = n(n+1)(2n+1)/6

and what you can do is find answer.~!!!!!!

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