A324938 - OEIS

A324938

a(n) = the number of values of m such that the sum of proper unitary divisors of m (A034460) is n.

0, 0, 0, 0, 1, 0, 2, 1, 2, 1, 3, 1, 3, 2, 3, 3, 2, 2, 3, 3, 4, 3, 2, 3, 3, 3, 4, 4, 3, 3, 3, 5, 4, 5, 4, 5, 2, 4, 4, 5, 4, 5, 3, 5, 5, 5, 2, 6, 3, 6, 4, 6, 3, 7, 3, 6, 4, 5, 3, 7, 3, 5, 4, 6, 2, 8, 2, 6, 5, 7, 2, 8, 4, 6, 7, 7, 4, 9, 2, 7, 4, 5, 4, 9, 3, 9

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OFFSET

2,7

COMMENTS

The unitary version of A048138.

The offset is 2 as in A048138 since there are infinitely many numbers (all the powers of primes) for which A034460 = 1.

LINKS

Amiram Eldar, Table of n, a(n) for n = 2..10000

FORMULA

a(A063948(n)) = 0.

EXAMPLE

a(8) = 2 since 8 is the sum of the proper unitary divisors of 10 (1 + 2 + 5) and 12 (1 + 3 + 4).

MATHEMATICA

us[1] = 0; us[n_] := Times @@ (1 + Power @@@ FactorInteger[n]) - n; m = 100; v = Table[0, {m}]; Do[u = us[k]; If[2 <= u <= m, v[[u]]++], {k, 1, m^2}]; Rest @ v

CROSSREFS

Cf. A034448, A034460, A048138, A063948.

Sequence in context: A138012 A072531 A025818 * A362181 A079413 A337787

Adjacent sequences: A324935 A324936 A324937 * A324939 A324940 A324941

KEYWORD

nonn

AUTHOR

Amiram Eldar, Sep 05 2019

STATUS

approved