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A347463
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Number of ordered factorizations of n with integer alternating product.
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25
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1, 1, 1, 2, 1, 1, 1, 3, 2, 1, 1, 4, 1, 1, 1, 7, 1, 4, 1, 4, 1, 1, 1, 6, 2, 1, 3, 4, 1, 1, 1, 11, 1, 1, 1, 18, 1, 1, 1, 6, 1, 1, 1, 4, 4, 1, 1, 20, 2, 4, 1, 4, 1, 6, 1, 6, 1, 1, 1, 8, 1, 1, 4, 26, 1, 1, 1, 4, 1, 1, 1, 35, 1, 1, 4, 4, 1, 1, 1, 20, 7, 1, 1, 8, 1
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OFFSET
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1,4
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COMMENTS
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An ordered factorization of n is a sequence of positive integers > 1 with product n.
We define the alternating product of a sequence (y_1,...,y_k) to be Product_i y_i^((-1)^(i-1)).
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LINKS
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FORMULA
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EXAMPLE
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The ordered factorizations for n = 4, 8, 12, 16, 24, 32, 36:
4 8 12 16 24 32 36
2*2 4*2 6*2 4*4 12*2 8*4 6*6
2*2*2 2*2*3 8*2 2*2*6 16*2 12*3
3*2*2 2*2*4 3*2*4 2*2*8 18*2
2*4*2 4*2*3 2*4*4 2*2*9
4*2*2 6*2*2 4*2*4 2*3*6
2*2*2*2 4*4*2 2*6*3
8*2*2 3*2*6
2*2*4*2 3*3*4
4*2*2*2 3*6*2
2*2*2*2*2 4*3*3
6*2*3
6*3*2
9*2*2
2*2*3*3
2*3*3*2
3*2*2*3
3*3*2*2
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MATHEMATICA
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facs[n_]:=If[n<=1, {{}}, Join@@Table[Map[Prepend[#, d]&, Select[facs[n/d], Min@@#>=d&]], {d, Rest[Divisors[n]]}]];
altprod[q_]:=Product[q[[i]]^(-1)^(i-1), {i, Length[q]}];
Table[Length[Select[Join@@Permutations/@facs[n], IntegerQ[altprod[#]]&]], {n, 100}]
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CROSSREFS
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The restriction to powers of 2 is A116406.
A046099 counts factorizations with no alternating permutations.
A103919 counts partitions by sum and alternating sum (reverse: A344612).
A119620 counts partitions with alternating product 1, ranked by A028982.
A273013 counts ordered factorizations of n^2 with alternating product 1.
A347438 counts factorizations with alternating product 1.
A347460 counts possible alternating products of factorizations.
Cf. A025047, A038548, A138364, A347440, A347441, A347453, A347454, A347456, A347458, A347459, A347464, A347705, A347708.
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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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