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 A218111 #22 Nov 20 2021 09:57:16
%S A218111 0,1,12,106,1035,11301,137774,1863044,27733869,451238935,7972318200,
%T A218111 152065270974,3115418734415,68245059703289,1591993733475570,
%U A218111 39406010771574856,1031649940977825633,28483179899706237483,827159099070697636124,25205610503231757308450
%N A218111 Number of transitive reflexive early confluent binary relations R on n+1 labeled elements with max_{x}(|{y : xRy}|) = n.
%C A218111 R is early confluent iff (xRy and xRz) implies (yRz or zRy) for all x, y, z.
%H A218111 Alois P. Heinz, <a href="/A218111/b218111.txt">Table of n, a(n) for n = 0..200</a> (terms n=23..100 from Vincenzo Librandi)
%F A218111 a(n) = A135313(n+1,n).
%F A218111 a(n) ~ n! * n^2 / (4 * log(2)^(n+2)). - _Vaclav Kotesovec_, Nov 20 2021
%p A218111 t:= proc(k) option remember; `if`(k<0, 0, unapply(exp(add(x^m/m! *t(k-m)(x), m=1..k)), x)) end: tt:= proc(k) option remember; unapply((t(k)-t(k-1))(x), x) end: T:= proc(n, k) option remember; coeff(series(tt(k)(x), x, n+1), x, n) *n! end:
%p A218111 a:= n-> T(n+1,n): seq(a(n), n=0..20);
%t A218111 t[k_] := t[k] = If[k < 0, 0&, Function[x, Evaluate @ Normal[Series[Exp[Sum[x^m/m!*t[k-m][x], {m, 1, k}]], {x, 0, k+2}]]]]; tt[k_] := tt[k] = Function[x, (t[k][x]-t[k-1][x]) // Evaluate]; T[n_, k_] := T[n, k] = Coefficient[Series[tt[k][x], {x, 0, n+1}], x, n]*n!; a[n_] := a[n] = T[n+1, n]; Table[a[n], {n, 0, 20}] (* _Jean-François Alcover_, Feb 17 2014, after Maple *)
%K A218111 nonn
%O A218111 0,3
%A A218111 _Alois P. Heinz_, Oct 20 2012