# Problem 443: GCD sequence
Let g(n) be a sequence defined as follows: g(4) = 13, g(n) = g(n-1) +
gcd(n, g(n-1)) for n > 4. The first few values are:
n4567891011121314151617181920...
g(n)1314161718272829303132333451545560... You are given that g(1 000) =
2524 and g(1 000 000) = 2624152. Find g(1015).