OFFSET
0,2
LINKS
Fausto A. C. Cariboni, Table of n, a(n) for n = 0..90
FORMULA
For n > 0, a(n) = A326495(n) + 1.
EXAMPLE
The a(0) = 1 through a(6) = 18 subsets:
{} {} {} {} {} {} {}
{1} {1} {1} {1} {1} {1}
{2} {2} {2} {2} {2}
{3} {3} {3} {3}
{2,3} {4} {4} {4}
{2,3} {5} {5}
{3,4} {2,3} {6}
{2,5} {2,3}
{3,4} {2,5}
{3,5} {2,6}
{4,5} {3,4}
{3,4,5} {3,5}
{4,5}
{4,6}
{5,6}
{2,5,6}
{3,4,5}
{4,5,6}
MATHEMATICA
Table[Length[Select[Subsets[Range[n]], Intersection[#, Union[Divide@@@Reverse/@Subsets[#, {2}], Subtract@@@Reverse/@Subsets[#, {2}]]]=={}&]], {n, 0, 10}]
PROG
(PARI)
a(n)={
my(recurse(k, b)=
if(k > n, 1,
my(t = self()(k + 1, b));
for(i=1, k\2, if(bittest(b, i) && (bittest(b, k-i) || (!(k%i) && bittest(b, k/i))), return(t)));
t += self()(k + 1, b + (1<<k));
t);
);
if(n, recurse(2, 0)) + 1;
} \\ Andrew Howroyd, Aug 25 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Jul 09 2019
EXTENSIONS
a(19)-a(41) from Andrew Howroyd, Aug 25 2019
STATUS
approved