A069289 - OEIS

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A069289

Sum of odd divisors of n <= sqrt(n).

1, 1, 1, 1, 1, 1, 1, 1, 4, 1, 1, 4, 1, 1, 4, 1, 1, 4, 1, 1, 4, 1, 1, 4, 6, 1, 4, 1, 1, 9, 1, 1, 4, 1, 6, 4, 1, 1, 4, 6, 1, 4, 1, 1, 9, 1, 1, 4, 8, 6, 4, 1, 1, 4, 6, 8, 4, 1, 1, 9, 1, 1, 11, 1, 6, 4, 1, 1, 4, 13, 1, 4, 1, 1, 9, 1, 8, 4, 1, 6, 13, 1, 1, 11, 6, 1, 4, 1

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OFFSET

1,9

COMMENTS

a(n) = Sum{d : d = A182469(n,k), d <= A000196(n), k=1..A001227(n)}. - Reinhard Zumkeller, Apr 05 2015

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

FORMULA

G.f.: Sum_{k>=1} (2*k - 1) * x^((2*k - 1)^2) / (1 - x^(2*k - 1)). - Ilya Gutkovskiy, Apr 04 2020

MATHEMATICA

Table[Total[Select[Divisors[n], OddQ[#]&&#<=Sqrt[n]&]], {n, 120}] (* Harvey P. Dale, Jul 16 2017 *)

PROG