A260152 - OEIS

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A260152

a(n) is the number of distinct sums s + t where s, t are divisors of n.

1, 3, 3, 6, 3, 9, 3, 10, 6, 10, 3, 16, 3, 10, 9, 15, 3, 19, 3, 20, 10, 10, 3, 26, 6, 10, 10, 20, 3, 28, 3, 21, 10, 10, 10, 33, 3, 10, 10, 32, 3, 32, 3, 21, 18, 10, 3, 40, 6, 21, 10, 21, 3, 33, 10, 32, 10, 10, 3, 50, 3, 10, 20, 28, 10, 33, 3, 21, 10, 34

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OFFSET

1,2

COMMENTS

s and t need not be distinct.

a(n) = 3 if and only if n is prime.

If p is prime, a(p^k) = A000217(k+1).

If p is in A005382, a(p*(2*p-1)) = 9. For all other members of A006881, a(n) = 10.

a(n) <= A000217(A000005(n)).

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

MathOverflow, A different kind of divisor sums