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
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
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Jan 28 2001
STATUS
approved