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%I #23 Aug 04 2018 23:01:39
%S 1,1,4,5,11,22,44,89,178,351,702,1413,2817,5634,11273,22542,45077,
%T 90150,180322,360621,721233,1442482,2884968,5769917,11539863,23079674,
%U 46159310,92318616,184637146,369274400,738548882,1477097703,2954195153,5908390134,11816780283
%N a(n) is the number of numbers k with 2^(n-1) < k <= 2^n having a number of divisors that is a power of 2.
%e a(5) = 11: The following 11 numbers have number of divisors which are powers of 2: 17,19,21,22,23,24,26,27,29,30,31 with 2,2,4,4,2,8,4,4,2,8,2 divisors respectively.
%o (PARI) a(n)=sum(k=2^(n-1)+1,2^n, my(d=numdiv(k)); (d/(1<<valuation(d,2)))==1 ); \\ _Joerg Arndt_, Feb 27 2017
%Y Cf. A037992.
%K nonn
%O 1,3
%A _Labos Elemer_
%E Name clarified and more terms from _Joerg Arndt_, Feb 27 2017
%E a(25)-a(28) from _Jon E. Schoenfield_, Jul 31 2018
%E a(29)-a(35) from _Jon E. Schoenfield_, Aug 04 2018
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