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A323525
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Number of ways to arrange the parts of a multiset whose multiplicities are the prime indices of n into a square matrix.
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6
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1, 1, 0, 0, 0, 0, 1, 0, 6, 4, 0, 12, 0, 0, 0, 24, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 36, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 84, 0, 0, 72, 0, 0, 0, 0, 0, 0, 0, 0, 126, 252, 0, 0, 0, 0, 0, 0
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OFFSET
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1,9
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COMMENTS
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This multiset (row n of A305936) is generally not the same as the multiset of prime indices of n. For example, the prime indices of 12 are {1,1,2}, while a multiset whose multiplicities are {1,1,2} is {1,1,2,3}.
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LINKS
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FORMULA
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If A056239(n) is a perfect square, a(n) = A318762(n). Otherwise, a(n) = 0.
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EXAMPLE
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The a(9) = 6 matrices:
[1 1] [1 2] [1 2] [2 1] [2 1] [2 2]
[2 2] [1 2] [2 1] [1 2] [2 1] [1 1]
The a(38) = 9 matrices:
[1 1 1] [1 1 1] [1 1 1] [1 1 1] [1 1 1] [1 1 1] [1 1 2] [1 2 1] [2 1 1]
[1 1 1] [1 1 1] [1 1 1] [1 1 2] [1 2 1] [2 1 1] [1 1 1] [1 1 1] [1 1 1]
[1 1 2] [1 2 1] [2 1 1] [1 1 1] [1 1 1] [1 1 1] [1 1 1] [1 1 1] [1 1 1]
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MATHEMATICA
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primeMS[n_]:=If[n==1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]];
nrmptn[n_]:=Join@@MapIndexed[Table[#2[[1]], {#1}]&, Reverse[primeMS[n]]];
Table[If[IntegerQ[Sqrt[Total[primeMS[n]]]], Length[Permutations[nrmptn[n]]], 0], {n, 100}]
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CROSSREFS
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The positions of 0's are numbers whose sum of prime indices is not a perfect square (A323527).
The positions of 1's are primes indexed by squares (A323526).
Cf. A008480, A026478, A056239, A103198, A112798, A120732, A318284, A318762, A323519, A323528, A323531.
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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