A380584 - OEIS

A380584

Number of positive integers <= n that have the same sum of odd divisors as n.

1, 2, 1, 3, 1, 2, 1, 4, 1, 2, 1, 3, 1, 2, 1, 5, 1, 2, 1, 3, 1, 2, 2, 4, 1, 2, 1, 3, 1, 3, 2, 6, 1, 2, 2, 3, 1, 2, 1, 4, 1, 3, 1, 3, 1, 4, 3, 5, 1, 2, 1, 3, 1, 2, 2, 4, 1, 2, 1, 5, 1, 4, 1, 7, 1, 4, 1, 3, 1, 5, 3, 4, 1, 2, 1, 3, 2, 2, 2, 5, 1, 2, 2, 5, 1, 2, 1, 4, 1, 2, 1, 6, 1, 6, 2, 6, 1, 2, 1, 3

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OFFSET

1,2

COMMENTS

Ordinal transform of A000593.

LINKS

Table of n, a(n) for n=1..100.

Eric Weisstein's World of Mathematics, Odd Divisor Function.

FORMULA

a(n) = |{j <= n : A000593(j) = A000593(n)}|.

MATHEMATICA

Table[Length[Select[Range[n], Sum[Mod[d, 2] d, {d, Divisors[#]}] == Sum[Mod[d, 2] d, {d, Divisors[n]}] &]], {n, 1, 100}]