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%I #16 Aug 16 2015 03:31:07
%S 1,-2,3,-12,15,45,-105,420,-1890,-4725,10395,31185,-135135,-315315,
%T -4729725,4729725,-80405325,-723647925,1527701175,7638505875,
%U 53469541125,117632990475,-245959889175,-737879667525,18446991688125,79936963981875,-2158298027510625
%N Numerator of 1/det(M) where M is the n X n matrix with M[i,j] = 1/gcd(i,j).
%C Negative terms for n: 2, 4, 7, 9, 10, 13, 14, 15, 17, 18, 23, 24, 27, 28, 30, ..., .
%t f[n_] := 1/Det[ Table[ 1/GCD[i, j], {i, n}, {j, n}]]; Numerator@ Array[f, 27]
%o (PARI) vector(40, n, numerator(1/matdet(matrix(n, n, i, j, 1/gcd(i, j))))) \\ _Michel Marcus_, Aug 06 2015
%Y Cf. A060841, A260909.
%K sign
%O 1,2
%A _Robert G. Wilson v_, Aug 04 2015