login
Heinz numbers of integer partitions into nonzero triangular numbers A000217.
1

%I #5 May 02 2019 16:04:29

%S 1,2,4,5,8,10,13,16,20,25,26,29,32,40,47,50,52,58,64,65,73,80,94,100,

%T 104,107,116,125,128,130,145,146,151,160,169,188,197,200,208,214,232,

%U 235,250,256,257,260,290,292,302,317,320,325,338,365,376,377,394,397

%N Heinz numbers of integer partitions into nonzero triangular numbers A000217.

%C The Heinz number of an integer partition (y_1,...,y_k) is prime(y_1)*...*prime(y_k).

%C The enumeration of these partitions by sum is given by A007294.

%e The sequence of terms together with their prime indices begins:

%e 1: {}

%e 2: {1}

%e 4: {1,1}

%e 5: {3}

%e 8: {1,1,1}

%e 10: {1,3}

%e 13: {6}

%e 16: {1,1,1,1}

%e 20: {1,1,3}

%e 25: {3,3}

%e 26: {1,6}

%e 29: {10}

%e 32: {1,1,1,1,1}

%e 40: {1,1,1,3}

%e 47: {15}

%e 50: {1,3,3}

%e 52: {1,1,6}

%e 58: {1,10}

%e 64: {1,1,1,1,1,1}

%e 65: {3,6}

%t nn=1000;

%t primeMS[n_]:=If[n==1,{},Flatten[Cases[FactorInteger[n],{p_,k_}:>Table[PrimePi[p],{k}]]]];

%t trgs=Table[n*(n+1)/2,{n,Sqrt[2*PrimePi[nn]]}];

%t Select[Range[nn],SubsetQ[trgs,primeMS[#]]&]

%Y Cf. A000217, A007294, A056239, A112798, A240026, A325327, A325360, A325362, A325367, A325390, A325394, A325400.

%K nonn

%O 1,2

%A _Gus Wiseman_, May 02 2019