N is a positive integer and F(N) denotes the sum of the base ten digits of N.

Derive an algorithm to determine the values of N such that F(2^N) is divisible by 10.

(In reply to continuation of Jer's table by Charlie)

Curiously there are only three values in the 1800's but sixteen in the 1300's. 
Actually in the whole range 1769 to 1892 there are only two.

Something's going on here.  They are certainly not as random as I would have guessed.

Posted by Jer on 2015-04-12 17:15:52