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%I #4 Mar 30 2012 18:50:37
%S 0,1,2,2,3,3,3,4,3,4,6,6,5,5,7,8,5,6,6,7,6,8,6,8,8,7,8,10,10,9,8,9,14,
%T 8,10,11,10,12,8,11,8,12,13,12,11,11,13,13,13,13,13,11,11,14,11,13,16,
%U 12,16,14,15,16,17,13,16,15,12,18,27,15,19,18,17,15,16,15,13,18,17,15
%N Number of times the n-th prime power can be written as an arithmetic mean of two other prime powers.
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/PrimePower.html">Prime Power</a>
%e n=7, A000961(7)=8=2^3: (3+13)/2=(A000961(3)+A000961(10))/2, (5+11)/2=(A000961(5)+A000961(9))/2 and (7+3^2)/2=(A000961(6)+A000961(8))/2: therefore a(7)=3.
%Y Cf. A000961, A071681.
%K nonn
%O 1,3
%A _Reinhard Zumkeller_, Aug 01 2003
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