A176803 - OEIS

%I #2 Mar 30 2012 19:00:24

%S 1,4,0,1,4,0,0,4,1,100,0,0,9,0,0,1,100,4,0,1,0,0,0,0,1,25,0,0,325,0

%N a(n) = the smallest natural numbers m such that product of antiharmonic mean of the divisors of n and antiharmonic mean of the divisors of m are integers, a(n) = 0 if no such number exists.

%C Antiharmonic mean of the divisors of number n is rational number b(n) = A001157(n) / A000203(n) = A158274(n) / A158275(n). a(n) = 1 for infinitely many n. a(n) = 1 for numbers from A020487: a(A020487(n)) = 1. a(n) = 1 iff A158275(n) = 1. a(n) = 0 for infinitely many n. a(n) = 0 for even A158275(n).

%e For n = 10; b(10) = 65/9, a(n) = 100 because b(100) = 63; 65/9 * 63 = 455 (integer).

%K nonn

%O 1,2

%A _Jaroslav Krizek_, Apr 26 2010