A174903 - OEIS

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A174903

Number of divisors d of n such that d<e<2*d for at least another divisor e of n.

0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 3, 0, 0, 1, 0, 0, 2, 0, 1, 0, 0, 0, 5, 0, 0, 0, 1, 0, 5, 0, 0, 0, 0, 1, 6, 0, 0, 0, 3, 0, 3, 0, 0, 3, 0, 0, 7, 0, 0, 0, 0, 0, 3, 0, 3, 0, 0, 0, 9, 0, 0, 1, 0, 0, 3, 0, 0, 0, 3, 0, 9, 0, 0, 2, 0, 1, 2, 0, 5, 0, 0, 0, 9, 0, 0, 0, 1, 0, 9, 1, 0, 0, 0, 0, 9, 0, 0, 1, 2, 0, 2, 0, 1, 4

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OFFSET

1,12

LINKS

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

FORMULA

a(A174905(n)) = 0; a(A005279(n)) > 0.

a(A174904(n)) = n and a(m) <> n for m < A174904(n).

a(m)*a(n) <= a(m*n) for m, n coprime.

EXAMPLE

a(12) = #{(2,3), (3,4), (4,6)} = 3;

a(15) = #{(3,5)} = 1;