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 A271421 #36 Feb 16 2025 08:33:33
%S A271421 1,4,119,23496,32149806,300214157831,19246160432331107,
%T A271421 8451529006578585976752,25443734373070679510011112460,
%U A271421 524973397889459587964008354031908560,74243674067972394056586805754940632245000310,71965837912588688126721254257169744333502564695515911
%N A271421 a(n) = fibonorial(3*n)/(fibonorial(2*n+1)*fibonorial(n+1)), where fibonorial(n) = A003266(n).
%D A271421 Steven R. Finch, Mathematical Constants, Cambridge, 2003, Section 1.2.5.
%H A271421 Simon Plouffe, <a href="http://www.plouffe.fr/simon/constants/fibofact.txt">Fibonacci factorials</a>.
%H A271421 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Fibonorial.html">Fibonorial</a>, <a href="https://mathworld.wolfram.com/FibonacciFactorialConstant.html">Fibonacci Factorial Constant</a>.
%F A271421 a(n) ~ 5*phi^(2*n^2 - 3*n - 2)/C where phi = (1+sqrt(5))/2, and C = (-1/phi^2; -1/phi^2)_inf is the Fibonacci factorial constant whose decimal expansion is given in A062073.
%t A271421 Table[Fibonorial[3 n]/(Fibonorial[2 n + 1] Fibonorial[n + 1]), {n, 1, 30}] (* The sequence itself *)
%t A271421 QPochhammer[-1/GoldenRatio^2] (* The Fibonacci factorial constant C in the asymptotic expansion *)
%Y A271421 Cf. A003266, A003267, A003268, A062073, A003150, A000045.
%K A271421 nonn,easy
%O A271421 1,2
%A A271421 _Vladimir Reshetnikov_, May 21 2016