A305736 - OEIS

A305736

Number of integer partitions of n whose greatest common divisor is composite (nonprime and > 1).

0, 0, 0, 1, 0, 1, 0, 2, 1, 1, 0, 4, 0, 1, 1, 5, 0, 4, 0, 8, 1, 1, 0, 14, 1, 1, 3, 16, 0, 10, 0, 22, 1, 1, 1, 41, 0, 1, 1, 45, 0, 18, 0, 57, 9, 1, 0, 94, 1, 8, 1, 102, 0, 38, 1, 138, 1, 1, 0, 221, 0, 1, 17, 231, 1, 59, 0, 298, 1, 22

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OFFSET

1,8

LINKS

Andrew Howroyd, Table of n, a(n) for n = 1..1000

FORMULA

a(n) = A018783(n) - A305735(n). - Andrew Howroyd, Jun 22 2018

EXAMPLE

The a(12) = 4 integer partitions are (12), (8 4), (6 6), (4 4 4).

MATHEMATICA

Table[Length[Select[IntegerPartitions[n], !(GCD@@#==1||PrimeQ[GCD@@#])&]], {n, 0, 20}]

PROG

(PARI) seq(n)={dirmul(vector(n, n, numbpart(n)), dirmul(vector(n, n, moebius(n)), vector(n, n, n>1&&!isprime(n))))} \\ Andrew Howroyd, Jun 22 2018

CROSSREFS

Cf. A000040, A000837, A018783, A100953, A289508, A302698, A305563, A305731, A305735.

Sequence in context: A124790 A325734 A351322 * A324642 A371740 A326757

Adjacent sequences: A305733 A305734 A305735 * A305737 A305738 A305739

KEYWORD

nonn

AUTHOR

Gus Wiseman, Jun 22 2018

STATUS

approved