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 A059381 Product J_2(i), i=1..n. 9
 1, 3, 24, 288, 6912, 165888, 7962624, 382205952, 27518828544, 1981355655168, 237762678620160, 22825217147535360, 3834636480785940480, 552187653233175429120, 106020029420769682391040, 20355845648787779019079680, 5862483546850880357494947840 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(n) is also the determinant of the symmetric n X n matrix M defined by M(i,j) = gcd(i,j)^2 for 1 <= i,j <= n. - Avi Peretz, (njk(AT)netvision.net.il), Mar 22 2001 REFERENCES L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 203, #17. LINKS G. C. Greubel, Table of n, a(n) for n = 1..250 Antal Bege, Hadamard product of GCD matrices, Acta Univ. Sapientiae, Mathematica, 1, 1 (2009) 43-49. FORMULA a(n) = A001088(n)*A175836(n). - Enrique Pérez Herrero, Oct 08 2011 MAPLE f:= n-> LinearAlgebra:-Determinant(Matrix(n, n, (i, j) -> igcd(i, j)^2)): map(f, [\$1..40]); # Robert Israel, Dec 01 2017 MATHEMATICA JordanTotient[n_, k_:1] := DivisorSum[n, #^k*MoebiusMu[n/#]&]/; (n>0)&&IntegerQ[n]; A059381[n_]:=Times@@(JordanTotient[#, 2]&/@Range[n] ); (* Enrique Pérez Herrero, Dec 29 2010 *) CROSSREFS Cf. A001088, A007434, A175836. Sequence in context: A257453 A128572 A052592 * A301933 A337027 A326001 Adjacent sequences: A059378 A059379 A059380 * A059382 A059383 A059384 KEYWORD nonn AUTHOR N. J. A. Sloane, Jan 28 2001 STATUS approved

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Last modified June 12 17:20 EDT 2024. Contains 373342 sequences. (Running on oeis4.)