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A359240
Number of divisors of 4*n-3 of form 4*k+3.
8
0, 0, 1, 0, 0, 2, 0, 0, 2, 0, 0, 2, 1, 0, 2, 0, 0, 2, 0, 2, 2, 0, 0, 2, 0, 0, 4, 0, 0, 2, 1, 0, 2, 2, 0, 2, 0, 0, 2, 0, 2, 4, 0, 0, 2, 0, 0, 4, 0, 0, 2, 0, 2, 2, 2, 0, 3, 0, 0, 2, 0, 2, 2, 2, 0, 2, 0, 0, 4, 0, 0, 4, 0, 0, 4, 2, 0, 2, 0, 0, 2, 0, 2, 2, 0, 2, 4, 0, 0, 4
OFFSET
1,6
LINKS
FORMULA
a(n) = A001842(4*n-3).
G.f.: Sum_{k>0} x^(3*k)/(1 - x^(4*k-1)).
MATHEMATICA
a[n_] := DivisorSum[4*n-3, 1 &, Mod[#, 4] == 3 &]; Array[a, 100] (* Amiram Eldar, Aug 23 2023 *)
PROG
(PARI) a(n) = sumdiv(4*n-3, d, d%4==3);
(PARI) my(N=100, x='x+O('x^N)); concat([0, 0], Vec(sum(k=1, N, x^(3*k)/(1-x^(4*k-1)))))
CROSSREFS
Cf. A001842.
Sequence in context: A096142 A216921 A344982 * A280285 A033719 A171608
KEYWORD
nonn,easy
AUTHOR
Seiichi Manyama, Dec 22 2022
STATUS
approved