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 A308717 #13 Sep 03 2025 09:11:26
%S A308717 3,0,4,0,1,9,1,5,5,1,6,4,2,5,5,3,0,7,5,6,0,1,8,6,0,0,2,7,9,0,0,7,5,7,
%T A308717 2,3,3,8,2,3,8,5,4,9,0,5,8,7,9,1,7,1,6,7,7,9,4,1,6,5,9,7,5,1,8,4,0,8,
%U A308717 8,5,3,9,2,5,2,3,3,2,0,4,4,1,9,6,5,1,4,6,1,8,2,9,9,0,2,5,5,0,2,1,9,7,1,1,2,0,4,8,3,0,3,9,2,2,3,1,0,5,0,6
%N A308717 Decimal expansion of cosh(sqrt(3)*Pi/2)*sech(Pi/2).
%H A308717 Kelvin Voskuijl, <a href="/A308717/b308717.txt">Table of n, a(n) for n = 1..20000</a>
%F A308717 Equals Product_{k>=0} (1 + 1/(2*k*(k + 1) + 1)).
%F A308717 Equals Product_{k>=0} (1 + 1/A001844(k)).
%e A308717 3.040191551642553075601860027900757233823854905879...
%t A308717 RealDigits[Cosh[Sqrt[3] Pi/2] Sech[Pi/2], 10, 120][[1]]
%o A308717 (PARI) cosh(sqrt(3)*Pi/2)/cosh(Pi/2) \\ _Michel Marcus_, Jun 20 2019
%Y A308717 Cf. A001844, A156648, A308642, A308718.
%K A308717 nonn,cons,changed
%O A308717 1,1
%A A308717 _Ilya Gutkovskiy_, Jun 19 2019