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A328871 Number of integer partitions of n whose distinct parts are pairwise indivisible (stable) and pairwise non-relatively prime (intersecting). 1

%I #6 Nov 12 2019 19:23:29

%S 1,1,2,2,3,2,4,2,4,3,5,2,6,2,7,5,7,2,10,2,11,7,14,2,16,4,19,8,22,2,30,

%T 3,29,14,37,8,48,4,50,19,59,5,82,4,81,28,93,8,128,9,128,38,147,8,199,

%U 19,196,52,223,12,308

%N Number of integer partitions of n whose distinct parts are pairwise indivisible (stable) and pairwise non-relatively prime (intersecting).

%C A partition with no two distinct parts divisible is said to be stable, and a partition with no two distinct parts relatively prime is said to be intersecting, so these are just stable intersecting partitions.

%e The a(1) = 1 through a(10) = 5 partitions (A = 10):

%e 1 2 3 4 5 6 7 8 9 A

%e 11 111 22 11111 33 1111111 44 333 55

%e 1111 222 2222 111111111 64

%e 111111 11111111 22222

%e 1111111111

%t stableQ[u_,Q_]:=!Apply[Or,Outer[#1=!=#2&&Q[#1,#2]&,u,u,1],{0,1}];

%t Table[Length[Select[IntegerPartitions[n],stableQ[Union[#],Divisible]&&stableQ[Union[#],GCD[#1,#2]==1&]&]],{n,0,30}]

%Y The Heinz numbers of these partitions are A329366.

%Y Replacing "intersecting" with "relatively prime" gives A328676.

%Y Stable partitions are A305148.

%Y Intersecting partitions are A328673.

%Y Cf. A000837, A285573, A303362, A305148, A316476, A328671, A328677.

%K nonn

%O 0,3

%A _Gus Wiseman_, Nov 12 2019

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