login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A318721 Number of strict relatively prime factorizations of n. 10
1, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1, 1, 1, 0, 2, 0, 1, 0, 1, 0, 4, 0, 0, 1, 1, 1, 2, 0, 1, 1, 2, 0, 4, 0, 1, 1, 1, 0, 2, 0, 1, 1, 1, 0, 2, 1, 2, 1, 1, 0, 6, 0, 1, 1, 0, 1, 4, 0, 1, 1, 4, 0, 4, 0, 1, 1, 1, 1, 4, 0, 2, 0, 1, 0, 6, 1, 1, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,24

COMMENTS

a(1) could be either 0 or 1.

LINKS

Table of n, a(n) for n=1..87.

EXAMPLE

The a(60) = 6 factorizations are (3*20), (4*15), (5*12), (2*3*10), (2*5*6), (3*4*5).

MATHEMATICA

strfacs[n_]:=If[n<=1, {{}}, Join@@Table[(Prepend[#1, d]&)/@Select[strfacs[n/d], Min@@#1>d&], {d, Rest[Divisors[n]]}]];

Table[Length[Select[strfacs[n], GCD@@#==1&]], {n, 50}]

CROSSREFS

Cf. A001055, A007716, A045778, A078374, A281116, A317748, A318720.

Sequence in context: A129308 A159200 A338021 * A219201 A341979 A331838

Adjacent sequences:  A318718 A318719 A318720 * A318722 A318723 A318724

KEYWORD

nonn

AUTHOR

Gus Wiseman, Sep 02 2018

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 1 00:13 EDT 2021. Contains 346377 sequences. (Running on oeis4.)