OFFSET
0,4
LINKS
Andrew Howroyd, Table of n, a(n) for n = 0..200
EXAMPLE
The a(4) = 20 chains:
24/1 24/2/1 24/4/2/1 24/8/4/2/1
24/3/1 24/6/2/1 24/12/4/2/1
24/4/1 24/6/3/1 24/12/6/2/1
24/6/1 24/8/2/1 24/12/6/3/1
24/8/1 24/8/4/1
24/12/1 24/12/2/1
24/12/3/1
24/12/4/1
24/12/6/1
MAPLE
b:= proc(n) option remember; 1 +
add(b(d), d=numtheory[divisors](n) minus {n})
end:
a:= n-> ceil(b(n!)/2):
seq(a(n), n=0..14); # Alois P. Heinz, Aug 23 2020
MATHEMATICA
chnsc[n_]:=Prepend[Join@@Table[Prepend[#, n]&/@chnsc[d], {d, DeleteCases[Divisors[n], 1|n]}], {n}];
Table[Length[chnsc[n!]], {n, 0, 5}]
CROSSREFS
A325617 is the maximal case.
A336941 is the version for superprimorials.
A337104 counts the case with distinct prime multiplicities.
A337071 is the case not necessarily ending with 1.
A000005 counts divisors.
A000142 lists factorial numbers.
A001055 counts factorizations.
A027423 counts divisors of factorial numbers.
A067824 counts chains of divisors starting with n.
A074206 counts chains of divisors from n to 1.
A076716 counts factorizations of factorial numbers.
A253249 counts chains of divisors.
KEYWORD
nonn
AUTHOR
Gus Wiseman, Aug 17 2020
EXTENSIONS
a(19)-a(20) from Alois P. Heinz, Aug 22 2020
STATUS
approved