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A359269
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Number of divisors of 5*n-2 of form 5*k+2.
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7
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0, 1, 0, 1, 0, 2, 0, 1, 0, 2, 0, 1, 1, 2, 0, 1, 0, 2, 0, 2, 0, 3, 0, 1, 0, 2, 1, 1, 0, 2, 1, 1, 0, 4, 0, 1, 0, 2, 0, 2, 1, 2, 0, 1, 0, 3, 0, 3, 1, 2, 0, 1, 0, 2, 1, 1, 0, 4, 0, 1, 0, 4, 0, 1, 1, 2, 1, 1, 1, 3, 0, 1, 0, 2, 0, 4, 0, 2, 0, 1, 0, 4, 1, 2, 1, 2, 0, 1, 0, 4
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OFFSET
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1,6
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COMMENTS
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Also number of divisors of 5*n-2 of form 5*k+4.
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LINKS
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FORMULA
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G.f.: Sum_{k>0} x^(2*k)/(1 - x^(5*k-1)).
G.f.: Sum_{k>0} x^(4*k-2)/(1 - x^(5*k-3)).
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MATHEMATICA
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a[n_] := DivisorSum[5*n-2, 1 &, Mod[#, 5] == 2 &]; Array[a, 100] (* Amiram Eldar, Aug 16 2023 *)
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PROG
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(PARI) a(n) = sumdiv(5*n-2, d, d%5==2);
(PARI) a(n) = sumdiv(5*n-2, d, d%5==4);
(PARI) my(N=100, x='x+O('x^N)); concat(0, Vec(sum(k=1, N, x^(2*k)/(1-x^(5*k-1)))))
(PARI) my(N=100, x='x+O('x^N)); concat(0, Vec(sum(k=1, N, x^(4*k-2)/(1-x^(5*k-3)))))
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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