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 A343161 #53 Jul 09 2025 04:55:56
%S A343161 1,1,1,2,3,5,8,14,24,42,72,127,221,390,684,1207,2125,3753,6620,11698,
%T A343161 20659,36518,64533,114099,201707,356683,630693,1115370,1972469,
%U A343161 3488489,6169656,10912003,19299555,34135099,60374747,106786342,188875933,334072759,590889162,1045136443
%N A343161 Number of planar distributive lattices with n nodes.
%H A343161 Andrew Howroyd, <a href="/A343161/b343161.txt">Table of n, a(n) for n = 1..1000</a>
%H A343161 Peter Jipsen, <a href="https://math.chapman.edu/~jipsen/mathposters/Planar%20distributive%20lattices%20up%20to%20size%2011.pdf">Planar distributive lattices up to size 11</a>, March 2014.
%H A343161 Peter Jipsen, <a href="https://math.chapman.edu/~jipsen/tikzsvg/planar-distributive-lattices15.html">Planar distributive lattices up to size 15</a>, March 2014.
%H A343161 Peter Jipsen, <a href="https://math.chapman.edu/~jipsen/tikzsvg/planar-vi-distributive-lattices.html">Planar vertically indecomposable distributive lattices up to size 22</a>, March 2014.
%F A343161 a(n) = Sum_{k=2..n} V(k)*a(n-k+1), where V(k) is the number of planar vertically indecomposable distributive lattices of size k. - _Bianca Newell_, Jun 22 2021
%F A343161 G.f.: x/(2 - B(x)/x) where B(x) is the g.f of A345734. - _Andrew Howroyd_, Jan 24 2023
%o A343161 (Python) v=[1,1,1,0,1,0,1,0,2,1,4,2,9,6,21,18,48,50,114,135,277,358,681]
%o A343161 p=[1,1,1]
%o A343161 for n in range(3,23):
%o A343161 p=p+[sum(v[k]*p[n-k+1] for k in range(2,n+1))]
%o A343161 p # _Bianca Newell_, Jun 22 2021
%o A343161 (PARI) V=concat(digits(1101010214296),[21,18,48,50,114,135,277,358,681]); P=List(1); for(n=2,#V,listput(P,V[2..n]*Colrev(P))); A343161=Vec(P) \\ _M. F. Hasler_, Jun 22 2021, using V[1..22] & formula from _Bianca Newell_
%o A343161 (PARI) \\ Needs S, V defined in A345734.
%o A343161 seq(n)={Vec(x/(1 - x - Ser((S(n)+V(n))/2)))} \\ _Andrew Howroyd_, Jan 24 2023
%Y A343161 Cf. A006966, A006982, A345734.
%K A343161 nonn
%O A343161 1,4
%A A343161 _N. J. A. Sloane_, Apr 18 2021, following a suggestion from _Allan C. Wechsler_
%E A343161 a(16)-a(22), computed with Python code, from _Bianca Newell_, Jun 22 2021
%E A343161 Terms a(23) and beyond from _Andrew Howroyd_, Jan 24 2023