OFFSET
1,4
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..10000
Antti Karttunen, Data supplement: n, a(n) computed for n = 1..100000
EXAMPLE
The a(60) = 8 factorizations are (2*2*3*5), (2*2*15), (3*4*5), (3*20), (4*15), (5*12), (6*10), (60). Missing from this list are (2*3*10), (2*5*6), (2*30).
MATHEMATICA
facs[n_]:=If[n<=1, {{}}, Join@@Table[Map[Prepend[#, d]&, Select[facs[n/d], Min@@#>=d&]], {d, Rest[Divisors[n]]}]];
Table[Length[Select[facs[n], Select[Tuples[Union[#], 2], UnsameQ@@#&&Divisible@@#&]=={}&]], {n, 100}]
PROG
(PARI)
pairwise_indivisible(v) = { for(i=1, #v, for(j=i+1, #v, if(!(v[j]%v[i]), return(0)))); (1); };
A305149(n, m=n, facs=List([])) = if(1==n, pairwise_indivisible(Set(facs)), my(s=0, newfacs); fordiv(n, d, if((d>1)&&(d<=m), newfacs = List(facs); listput(newfacs, d); s += A305149(n/d, d, newfacs))); (s)); \\ Antti Karttunen, Oct 08 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, May 26 2018
EXTENSIONS
More terms from Antti Karttunen, Oct 08 2018
STATUS
approved