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A347440
Number of factorizations of n with alternating product < 1.
22
0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 2, 0, 1, 1, 1, 0, 2, 0, 2, 1, 1, 0, 4, 0, 1, 1, 2, 0, 3, 0, 3, 1, 1, 1, 3, 0, 1, 1, 4, 0, 3, 0, 2, 2, 1, 0, 6, 0, 2, 1, 2, 0, 4, 1, 4, 1, 1, 0, 6, 0, 1, 2, 3, 1, 3, 0, 2, 1, 3, 0, 8, 0, 1, 2, 2, 1, 3, 0, 6, 1, 1, 0, 6, 1, 1, 1
OFFSET
1,12
COMMENTS
All such factorizations have even length and alternating sum < 0, so partitions of this type are counted by A344608.
Also the number of factorizations of n with alternating sum < 0.
A factorization of n is a weakly increasing 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)).
FORMULA
a(2^n) = A344608(n).
a(n) = A339846(n) - A347438(n).
EXAMPLE
The a(n) factorizations for n = 6, 12, 24, 30, 48, 72, 96, 120:
2*3 2*6 3*8 5*6 6*8 8*9 2*48 2*60
3*4 4*6 2*15 2*24 2*36 3*32 3*40
2*12 3*10 3*16 3*24 4*24 4*30
2*2*2*3 4*12 4*18 6*16 5*24
2*2*2*6 6*12 8*12 6*20
2*2*3*4 2*2*2*9 2*2*3*8 8*15
2*2*3*6 2*2*4*6 10*12
2*3*3*4 2*3*4*4 2*2*5*6
2*2*2*12 2*3*4*5
2*2*2*2*2*3 2*2*2*15
2*2*3*10
MATHEMATICA
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[facs[n], altprod[#]<1&]], {n, 100}]
CROSSREFS
Positions of 0's are A000430.
Positions of 2's are A054753.
Positions of non-0's are A080257.
Positions of 1's are A332269.
The weak version (<= 1 instead of < 1) is A339846, ranked by A028982.
The reciprocal version is A339890.
The additive version is A344608, ranked by A119899.
The even-sum additive version is A344743, ranked by A119899 /\ A300061.
Allowing any integer alternating product gives A347437, additive A347446.
The equal version (= 1 instead of < 1) is A347438.
Allowing any integer reciprocal alternating product gives A347439.
The complement (>= 1 instead of < 1) is counted by A347456.
A038548 counts possible reverse-alternating products of factorizations.
A046099 counts factorizations with no alternating permutations.
A071321 gives the alternating sum of prime factors (reverse: A071322).
A236913 counts partitions of 2n with reverse-alternating sum <= 0.
A273013 counts ordered factorizations of n^2 with alternating product 1.
A347460 counts possible alternating products of factorizations.
Sequence in context: A086971 A341677 A211159 * A088434 A205745 A333781
KEYWORD
nonn
AUTHOR
Gus Wiseman, Sep 07 2021
STATUS
approved