OFFSET
0,2
LINKS
Andrew Howroyd, Table of n, a(n) for n = 0..200
MATHEMATICA
multsubs[set_, k_]:=If[k==0, {{}}, Join@@Table[Prepend[#, set[[i]]]&/@multsubs[Drop[set, i-1], k-1], {i, Length[set]}]];
csm[s_]:=With[{c=Select[Tuples[Range[Length[s]], 2], And[OrderedQ[#], UnsameQ@@#, Length[Intersection@@s[[#]]]>0]&]}, If[c=={}, s, csm[Union[Append[Delete[s, List/@c[[1]]], Union@@s[[c[[1]]]]]]]]];
Table[Length[Select[Subsets[multsubs[Range[n+1], 2], {n}], And[Union@@#==Range[Max@@Union@@#], Length[csm[#]]==1]&]], {n, 5}]
PROG
(PARI)
Connected(v)={my(u=vector(#v)); for(n=1, #u, u[n]=v[n] - sum(k=1, n-1, binomial(n-1, k)*v[k]*u[n-k])); u}
seq(n)={Vec(vecsum(Connected(vector(2*n, j, (1 + x + O(x*x^n))^binomial(j+1, 2)))))} \\ Andrew Howroyd, Nov 28 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Nov 28 2018
EXTENSIONS
Terms a(7) and beyond from Andrew Howroyd, Nov 28 2018
STATUS
approved