login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A347048 Number of even-length ordered factorizations of n with integer alternating product. 2
1, 0, 0, 1, 0, 0, 0, 1, 1, 0, 0, 1, 0, 0, 0, 3, 0, 1, 0, 1, 0, 0, 0, 1, 1, 0, 1, 1, 0, 0, 0, 4, 0, 0, 0, 7, 0, 0, 0, 1, 0, 0, 0, 1, 1, 0, 0, 6, 1, 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 1, 11, 0, 0, 0, 1, 0, 0, 0, 11, 0, 0, 1, 1, 0, 0, 0, 6, 3, 0, 0, 1, 0, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,16
COMMENTS
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)).
LINKS
FORMULA
a(n) = A347463(n) - A347049(n).
EXAMPLE
The a(n) ordered factorizations for n = 16, 32, 36, 48, 64, 96:
4*4 8*4 6*6 12*4 8*8 24*4
8*2 16*2 12*3 24*2 16*4 48*2
2*2*2*2 2*2*4*2 18*2 2*2*6*2 32*2 3*2*8*2
4*2*2*2 2*2*3*3 3*2*4*2 2*2*4*4 4*2*6*2
2*3*3*2 4*2*3*2 2*2*8*2 6*2*4*2
3*2*2*3 6*2*2*2 2*4*4*2 8*2*3*2
3*3*2*2 4*2*2*4 12*2*2*2
4*2*4*2 2*2*12*2
4*4*2*2
8*2*2*2
2*2*2*2*2*2
MATHEMATICA
ordfacs[n_]:=If[n<=1, {{}}, Join@@Table[Prepend[#, d]&/@ordfacs[n/d], {d, Rest[Divisors[n]]}]];
altprod[q_]:=Product[q[[i]]^(-1)^(i-1), {i, Length[q]}];
Table[Length[Select[ordfacs[n], EvenQ[Length[#]]&&IntegerQ[altprod[#]]&]], {n, 100}]
CROSSREFS
Positions of 0's are A005117 \ {2}.
The restriction to powers of 2 is A027306.
Heinz numbers of partitions of this type are A028260 /\ A347457.
Positions of 3's appear to be A030514.
Positions of 1's are 1 and A082293.
Allowing non-integer alternating product gives A174725, unordered A339846.
The odd-length version is A347049.
The unordered version is A347438, reverse A347439.
Allowing any length gives A347463.
Partitions of this type are counted by A347704, reverse A035363.
A001055 counts factorizations (strict A045778, ordered A074206).
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.
A339890 counts odd-length factorizations, ordered A174726.
A347050 = factorizations with alternating permutation, complement A347706.
A347437 = factorizations with integer alternating product, reverse A347442.
A347446 = partitions with integer alternating product, reverse A347445.
A347460 counts possible alternating products of factorizations.
Sequence in context: A346012 A317946 A347439 * A140807 A232629 A340007
KEYWORD
nonn
AUTHOR
Gus Wiseman, Oct 10 2021
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 28 20:05 EDT 2024. Contains 371254 sequences. (Running on oeis4.)