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A039593 Number of unitary divisors of central binomial coefficients. 3


%S 1,2,2,4,4,4,4,8,8,8,16,16,16,16,16,32,32,32,32,32,64,64,64,64,64,64,

%T 64,64,128,128,128,256,256,256,512,512,512,512,1024,1024,1024,1024,

%U 1024,1024,512,512,1024,1024,1024,1024,1024,1024,1024,1024,4096,4096

%N Number of unitary divisors of central binomial coefficients.

%C As in A034444, all terms are powers of 2.

%H Amiram Eldar, <a href="/A039593/b039593.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A034444(A001405(n)) = 2^A034973(n).

%e At n=5, the central binomial coefficient is 10, having 4 divisors, each of which is unitary, so a(5)=4.

%t a[n_] := 2^PrimeNu[Binomial[n, Floor[n/2]]]; Array[a, 56] (* _Amiram Eldar_, Oct 06 2019 *)

%Y Cf. A001405, A034444, A034973.

%K nonn

%O 1,2

%A _Labos Elemer_

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Last modified January 29 10:34 EST 2020. Contains 331337 sequences. (Running on oeis4.)