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%I #13 Nov 29 2016 03:01:50
%S 26,30,55,58,59,62,74,78,80,84,100,108,112,113,117,124,126,135,153,
%T 187,191,200,205,258,265,280,291,310,317,323,336,337,342,344,351,352,
%U 353,358,359,365,374,380,384,404,409,416,444,445,458,481,485,492,501,503
%N Numbers n such that A000041(n) is of the form 2^2 * k for odd k.
%C Numbers n such that A278478(n) = 2.
%C Also numbers n such that A000041(n) has twice as many even divisors as odd divisors.
%H Colin Barker, <a href="/A278779/b278779.txt">Table of n, a(n) for n = 1..1000</a>
%F A000041(a(n)) = A278196(n).
%o (PARI) isok(n) = valuation(numbpart(n), 2)==2;
%o select(n->isok(n), vector(1000, n, n))
%Y Cf. A000041, A278196, A278780, A278781, A278782, A278783, A278784.
%Y Positions of 2's in A278478.
%K nonn
%O 1,1
%A _Colin Barker_, Nov 28 2016
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