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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A320732 Number of factorizations of n into primes or semiprimes. 27
 1, 1, 1, 2, 1, 2, 1, 2, 2, 2, 1, 3, 1, 2, 2, 3, 1, 3, 1, 3, 2, 2, 1, 4, 2, 2, 2, 3, 1, 4, 1, 3, 2, 2, 2, 6, 1, 2, 2, 4, 1, 4, 1, 3, 3, 2, 1, 5, 2, 3, 2, 3, 1, 4, 2, 4, 2, 2, 1, 7, 1, 2, 3, 4, 2, 4, 1, 3, 2, 4, 1, 7, 1, 2, 3, 3, 2, 4, 1, 5, 3, 2, 1, 7, 2, 2, 2 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 LINKS EXAMPLE The a(60) = 5 factorizations are (2*2*3*5), (2*2*15), (2*3*10), (2*5*6), (3*4*5), (4*15), (6*10). MATHEMATICA psemfacs[n_]:=If[n<=1, {{}}, Join@@Table[Map[Prepend[#, d]&, Select[psemfacs[n/d], Min@@#>=d&]], {d, Select[Rest[Divisors[n]], PrimeOmega[#]<=2&]}]]; Table[Length[psemfacs[n]], {n, 100}] CROSSREFS Cf. A001055, A001222, A001358, A007716, A007717, A037143, A045778, A320663, A320655. Sequence in context: A327399 A122375 A038548 * A305149 A336737 A327400 Adjacent sequences:  A320729 A320730 A320731 * A320733 A320734 A320735 KEYWORD nonn AUTHOR Gus Wiseman, Oct 20 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.

Last modified September 20 14:44 EDT 2021. Contains 347586 sequences. (Running on oeis4.)