OFFSET
1,2
COMMENTS
The divisor lattice D(n) is the lattice of the divisors of the natural number n.
LINKS
Eric M. Schmidt, Table of n, a(n) for n = 1..10000
EXAMPLE
From Gus Wiseman, Aug 24 2018: (Start)
The a(120) = 6 antichains:
{8,12,20,30}
{8,12,15,20}
{8,10,12,15}
{6,8,15,20}
{6,8,10,15}
{4,6,10,15}
(End)
PROG
(Sage)
def A096826(n) :
if n==1 : return 1
R.<t> = QQ[]; mults = [x[1] for x in factor(n)]
maxsize = prod((t^(m+1)-1)//(t-1) for m in mults)[sum(mults)//2]
dlat = LatticePoset((divisors(n), attrcall("divides")))
count = 0
for ac in dlat.antichains_iterator() :
if len(ac) == maxsize : count += 1
return count
# Eric M. Schmidt, May 13 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Yuval Dekel (dekelyuval(AT)hotmail.com), Aug 17 2004
EXTENSIONS
More terms from Eric M. Schmidt, May 13 2013
STATUS
approved