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 A325392 Number of permutations of the multiset of prime factors of n whose first part is not 2. 2

%I

%S 1,0,1,0,1,1,1,0,1,1,1,1,1,1,2,0,1,2,1,1,2,1,1,1,1,1,1,1,1,4,1,0,2,1,

%T 2,3,1,1,2,1,1,4,1,1,3,1,1,1,1,2,2,1,1,3,2,1,2,1,1,6,1,1,3,0,2,4,1,1,

%U 2,4,1,4,1,1,3,1,2,4,1,1,1,1,1,6,2,1,2

%N Number of permutations of the multiset of prime factors of n whose first part is not 2.

%F If n is odd, a(n) = A008480(n). If n is even, a(n) = A008480(n) - A008480(n/2).

%e The a(90) = 9 permutations of {2,3,3,5} not starting with 2:

%e 3 2 3 5

%e 3 2 5 3

%e 3 3 2 5

%e 3 3 5 2

%e 3 5 2 3

%e 3 5 3 2

%e 5 2 3 3

%e 5 3 2 3

%e 5 3 3 2

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

%t Table[Length[Select[Permutations[primeMS[n]],#=={}||First[#]>1&]],{n,100}]

%Y Number of times n appears in A325390.

%Y Cf. A008480, A056239, A112798, A325327, A325362, A325364, A325367, A325403, A325407, A325460, A325461.

%K nonn

%O 1,15

%A _Gus Wiseman_, May 02 2019

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Last modified February 23 16:15 EST 2020. Contains 332174 sequences. (Running on oeis4.)