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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A254578 Number of ordered factorizations into distinct factors. 5
 1, 1, 1, 1, 1, 3, 1, 3, 1, 3, 1, 5, 1, 3, 3, 3, 1, 5, 1, 5, 3, 3, 1, 13, 1, 3, 3, 5, 1, 13, 1, 5, 3, 3, 3, 13, 1, 3, 3, 13, 1, 13, 1, 5, 5, 3, 1, 21, 1, 5, 3, 5, 1, 13, 3, 13, 3, 3, 1, 29, 1, 3, 5, 11, 3, 13, 1, 5, 3, 13, 1, 29, 1, 3, 5, 5, 3, 13, 1, 21, 3, 3 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,6 LINKS Alois P. Heinz, Table of n, a(n) for n = 1..10000 Arnold Knopfmacher and Michael Mays, Ordered and Unordered Factorizations of Integers, The Mathematica Journal, Vol 10 (1). EXAMPLE a(20)=5 because there are 5 ordered factorizations of 20 into distinct factors: 2*10, 4*5, 5*4, 10*2, 20. MAPLE with(numtheory): b:= proc(n, i, p) option remember; `if`(n<=i, (p+1)!, 0)+add( b(n/d, d-1, p+1), d=select(x->x<=i, divisors(n)minus{1, n})) end: a:= n-> b(n\$2, 0): seq(a(n), n=1..100); # Alois P. Heinz, Feb 01 2015 MATHEMATICA f[n_] := f[n] = Level[Table[Map[Prepend[#, d] &, f[n/d]], {d, Rest[Divisors[n]]}], {2}]; f[1] = {{}}; Map[Length, Map[Select[#, Apply[Unequal, #] &] &, Table[f[n], {n, 1, 60}]]] CROSSREFS Cf. A074206, A254577, A251683. Sequence in context: A294786 A294787 A294788 * A348610 A296120 A050345 Adjacent sequences: A254575 A254576 A254577 * A254579 A254580 A254581 KEYWORD nonn AUTHOR Geoffrey Critzer, Feb 01 2015 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.

Last modified September 11 08:57 EDT 2024. Contains 375814 sequences. (Running on oeis4.)