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GCD sequence

Problem 443

Published on 02 November 2013 at 04:00 pm [Server Time]

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:

n 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 ...
g(n) 13 14 16 17 18 27 28 29 30 31 32 33 34 51 54 55 60 ...

You are given that g(1 000) = 2524 and g(1 000 000) = 2624152.

Find g(1015).


Answer:
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