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%I #12 Nov 29 2016 02:55:59
%S 15,106,122,131,136,253,295,327,339,383,412,449,465,517,520,551,580,
%T 581,599,602,632,648,669,677,776,806,815,838,904,927,1071,1137,1166,
%U 1174,1199,1263,1275,1298,1325,1375,1399,1404,1425,1554,1564,1641,1684,1688
%N Numbers n such that A000041(n) is of the form 2^4 * k for odd k.
%C Numbers n such that A278478(n) = 4.
%C Also numbers n such that A000041(n) has four times as many even divisors as odd divisors.
%H Colin Barker, <a href="/A278781/b278781.txt">Table of n, a(n) for n = 1..600</a>
%F A000041(a(n)) = A278198(n).
%o (PARI) isok(n) = valuation(numbpart(n), 2)==4;
%o select(n->isok(n), vector(2000, n, n))
%Y Cf. A000041, A278198, A278779, A278780, A278782, A278783, A278784.
%Y Positions of 4's in A278478.
%K nonn
%O 1,1
%A _Colin Barker_, Nov 28 2016
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