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Numerator of det(M) where M is the n X n matrix with M[i,j] = 1/lcm(i,j).
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%I #23 Aug 24 2015 17:28:34

%S 1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,

%T 2,1,2,1,8,2,16,16,32,8,64,32,64,4,8,8,256,128,512,256,2048,256,1024,

%U 1024,2048,2048,8192,4096,16384,128,2048,2048,4096,8192,32768,65536,131072,16384,131072

%N Numerator of det(M) where M is the n X n matrix with M[i,j] = 1/lcm(i,j).

%C All terms are powers of two (A000079).

%H Robert G. Wilson v, <a href="/A260897/b260897.txt">Table of n, a(n) for n = 1..500</a>

%F a(n) = 2^A260502(n).

%p seq(denom(1/LinearAlgebra:-Determinant(Matrix(n,n,1/ilcm))),n=1..100); # _Robert Israel_, Aug 17 2015

%t f[n_] := Denominator[1 / Det[ Table[ 1/LCM[i, j], {i, n}, {j, n}]]]; Array[f, 73]

%o (PARI) vector(80, n, denominator(1/matdet(matrix(n, n, i, j, 1/lcm(i, j))))) \\ _Michel Marcus_, Aug 04 2015

%Y Cf. A060841, A260502.

%K nonn

%O 1,35

%A _Robert G. Wilson v_, Aug 03 2015