This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A326279 #4 Jun 25 2019 10:10:36
%S A326279 0,0,0,0,28,864,32064,2094064
%N A326279 Number of labeled n-vertex simple graphs containing either a crossing or a nesting pair of edges.
%C A326279 Two edges {a,b}, {c,d} are crossing if a < c < b < d or c < a < d < b, and nesting if a < c < d < b or c < a < b < d.
%F A326279 A006125(n) = a(n) + A326244(n).
%e A326279 The a(4) = 28 edge-sets:
%e A326279 {13,24} {12,13,24} {12,13,14,23} {12,13,14,23,24} {12,13,14,23,24,34}
%e A326279 {14,23} {12,14,23} {12,13,14,24} {12,13,14,23,34}
%e A326279 {13,14,23} {12,13,23,24} {12,13,14,24,34}
%e A326279 {13,14,24} {12,13,24,34} {12,13,23,24,34}
%e A326279 {13,23,24} {12,14,23,24} {12,14,23,24,34}
%e A326279 {13,24,34} {12,14,23,34} {13,14,23,24,34}
%e A326279 {14,23,24} {13,14,23,24}
%e A326279 {14,23,34} {13,14,23,34}
%e A326279 {13,14,24,34}
%e A326279 {13,23,24,34}
%e A326279 {14,23,24,34}
%t A326279 croXQ[stn_]:=MatchQ[stn,{___,{x_,y_},___,{z_,t_},___}/;x<z<y<t||z<x<t<y];
%t A326279 nesXQ[stn_]:=MatchQ[stn,{___,{x_,y_},___,{z_,t_},___}/;x<z<t<y||z<x<y<t];
%t A326279 Table[Length[Select[Subsets[Subsets[Range[n],{2}]],croXQ[#]||nesXQ[#]&]],{n,0,5}]
%Y A326279 Crossing and nesting simple graphs are (both) A326210, while non-crossing, non-nesting simple graphs are A326244.
%Y A326279 Cf. A000108, A001519, A006125, A016098, A054726, A095661, A324170.
%Y A326279 Cf. A326209, A326211, A326248, A326250, A326256.
%K A326279 nonn,more
%O A326279 0,5
%A A326279 _Gus Wiseman_, Jun 23 2019