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 A323949 #16 Feb 10 2019 19:01:20
%S A323949 1,1,2,4,10,36,145,631,3015,15563,86144,508311,3180930,21018999,
%T A323949 146111543,1065040886,8117566366,64531949885,533880211566,
%U A323949 4587373155544,40865048111424,376788283806743,3590485953393739,35312436594162173,357995171351223109,3736806713651177702
%N A323949 Number of set partitions of {1, ..., n} with no block containing three distinct cyclically successive vertices.
%C A323949 Cyclically successive means 1 is a successor of n.
%H A323949 Alois P. Heinz, <a href="/A323949/b323949.txt">Table of n, a(n) for n = 0..250</a>
%e A323949 The a(1) = 1 through a(4) = 10 set partitions:
%e A323949 {{1}} {{1,2}} {{1},{2,3}} {{1,2},{3,4}}
%e A323949 {{1},{2}} {{1,2},{3}} {{1,3},{2,4}}
%e A323949 {{1,3},{2}} {{1,4},{2,3}}
%e A323949 {{1},{2},{3}} {{1},{2},{3,4}}
%e A323949 {{1},{2,3},{4}}
%e A323949 {{1,2},{3},{4}}
%e A323949 {{1},{2,4},{3}}
%e A323949 {{1,3},{2},{4}}
%e A323949 {{1,4},{2},{3}}
%e A323949 {{1},{2},{3},{4}}
%t A323949 spsu[_,{}]:={{}};spsu[foo_,set:{i_,___}]:=Join@@Function[s,Prepend[#,s]&/@spsu[Select[foo,Complement[#,Complement[set,s]]=={}&],Complement[set,s]]]/@Cases[foo,{i,___}];
%t A323949 Table[Length[spsu[Select[Subsets[Range[n]],Select[Partition[Range[n],3,1,1],Function[ed,UnsameQ@@ed&&Complement[ed,#]=={}]]=={}&],Range[n]]],{n,8}]
%Y A323949 Cf. A000085, A000110, A000126, A000296, A000325, A001610, A001644, A078012, A169985.
%Y A323949 Cf. A306351, A306357, A323950, A323951, A323953, A323954, A323955, A323956.
%K A323949 nonn
%O A323949 0,3
%A A323949 _Gus Wiseman_, Feb 10 2019
%E A323949 a(12)-a(25) from _Alois P. Heinz_, Feb 10 2019