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A357260
a(n) is the number of 2 X 2 Euclid-reduced matrices having coprime elements and determinant n.
1
1, 2, 3, 4, 5, 8, 7, 9, 9, 14, 11, 16, 13, 20, 18, 19, 17, 28, 19, 26, 26, 32, 23, 36, 25, 38, 31, 38, 29, 54, 31, 41, 42, 50, 38, 56, 37, 56, 50, 56, 41, 76, 43, 62, 58, 68, 47, 78, 49, 78, 66, 74, 53, 92, 62, 76, 74, 86, 59, 114, 61, 92, 78, 85, 74, 124, 67, 98, 90, 118
OFFSET
1,2
COMMENTS
See Bacher link for the definition of Euclid-reduced.
FORMULA
a(n) = Sum_{d^2|n} moebius(d)*A357259(n/d^2).
MATHEMATICA
f[n_] := DivisorSum[n, # + 1 - n/# &, #^2 >= n &]; a[n_] := DivisorSum[n, MoebiusMu[Sqrt[#]] * f[n/#] &, IntegerQ[Sqrt[#]] &]; Array[a, 100] (* Amiram Eldar, Sep 21 2022 *)
PROG
(PARI) f(n) = sumdiv(n, d, if (d^2 >= n, d + 1 -n/d)); \\ A357259
a(n) = sumdiv(n, d, if (issquare(d), moebius(sqrtint(d))*f(n/d)));
CROSSREFS
Cf. A357259.
Sequence in context: A319605 A352047 A245822 * A069797 A158979 A233249
KEYWORD
nonn
AUTHOR
Michel Marcus, Sep 21 2022
STATUS
approved