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 A387202 #37 Aug 28 2025 05:08:52
%S A387202 1,5,21,87,363,1534,6570,28492,124944,553301,2471373,11122275,
%T A387202 50389695,229643895,1052093655,4842863465,22386911925,103885321615,
%U A387202 483759492255,2259888333445,10587902977185,49738841822400,234235771140876,1105609645231322,5229610939919718
%N A387202 a(n) is the number of dissections of a (4*n+2)-gon into hexagons using strictly disjoint diagonals.
%H A387202 Muhammed Sefa Saydam, <a href="/A387202/b387202.txt">Table of n, a(n) for n = 1..100</a>
%F A387202 G.f.: x*(1 + 4*B(x) + 3*B(x)^2) + B(x)^2, where 1 + B(x) is the g.f. of A002212. - _Andrew Howroyd_, Aug 21 2025
%F A387202 D-finite with recurrence -(n+2)*(2*n-3)*a(n) +3*(2*n+1)*(2*n-3)*a(n-1) -5*(2*n+1)*(n-3)*a(n-2)=0. - _R. J. Mathar_, Aug 28 2025
%o A387202 (PARI) seq(n)={my(g=(1 - 3*x - sqrt(1 - 6*x + 5*x^2 + O(x*x^n)))/(2*x)); Vec((1 + 4*g + 3*g^2)*x + g^2)} \\ _Andrew Howroyd_, Aug 21 2025
%Y A387202 Cf. A002212, A093128.
%K A387202 nonn,new
%O A387202 1,2
%A A387202 _Muhammed Sefa Saydam_, Aug 21 2025