cp's OEIS Frontend

A367869 Number of labeled simple graphs covering n vertices and satisfying a strict version of the axiom of choice.

%I A367869 #11 Dec 30 2023 17:38:56
%S A367869 1,0,1,4,34,387,5596,97149,1959938,44956945,1154208544,32772977715,
%T A367869 1019467710328,34473686833527,1259038828370402,49388615245426933,
%U A367869 2070991708598960524,92445181295983865757,4376733266230674345874,219058079619119072854095,11556990682657196214302036
%N A367869 Number of labeled simple graphs covering n vertices and satisfying a strict version of the axiom of choice.
%C A367869 The axiom of choice says that, given any set of nonempty sets Y, it is possible to choose a set containing an element from each. The strict version requires this set to have the same cardinality as Y, meaning no element is chosen more than once.
%C A367869 Number of labeled n-node graphs with at most one cycle in each component and no isolated vertices. - _Andrew Howroyd_, Dec 30 2023
%H A367869 Andrew Howroyd, <a href="/A367869/b367869.txt">Table of n, a(n) for n = 0..200</a>
%F A367869 E.g.f.: exp(B(x) - x - 1) where B(x) is the e.g.f. of A129271. - _Andrew Howroyd_, Dec 30 2023
%e A367869 The a(3) = 4 graphs:
%e A367869   {{1,2},{1,3}}
%e A367869   {{1,2},{2,3}}
%e A367869   {{1,3},{2,3}}
%e A367869   {{1,2},{1,3},{2,3}}
%t A367869 Table[Length[Select[Subsets[Subsets[Range[n],{2}]], Union@@#==Range[n]&&Select[Tuples[#], UnsameQ@@#&]!={}&]],{n,0,5}]
%o A367869 (PARI) seq(n)={my(t=-lambertw(-x + O(x*x^n))); Vec(serlaplace(sqrt(1/(1-t))*exp(t/2 - 3*t^2/4 - x)))} \\ _Andrew Howroyd_, Dec 30 2023
%Y A367869 The connected case is A129271.
%Y A367869 The non-covering case is A133686, complement A367867.
%Y A367869 The complement is A367868, connected A140638 (unlabeled A140636).
%Y A367869 A001187 counts connected graphs, A001349 unlabeled.
%Y A367869 A006125 counts graphs, A000088 unlabeled.
%Y A367869 A006129 counts covering graphs, A002494 unlabeled.
%Y A367869 A058891 counts set-systems, unlabeled A000612, without singletons A016031.
%Y A367869 A059201 counts covering T_0 set-systems, unlabeled A319637, ranks A326947.
%Y A367869 A143543 counts simple labeled graphs by number of connected components.
%Y A367869 Cf. A057500, A116508, A355740, A367770, A367863, A367902.
%K A367869 nonn
%O A367869 0,4
%A A367869 _Gus Wiseman_, Dec 08 2023
%E A367869 Terms a(7) and beyond from _Andrew Howroyd_, Dec 30 2023