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 A088539 #34 Dec 17 2024 03:28:35
%S A088539 9,4,6,8,0,6,4,0,7,1,8,0,0,7,9,3,3,4,2,1,6,0,9,4,4,1,3,1,0,9,7,5,6,2,
%T A088539 3,3,2,5,0,0,6,9,5,0,2,6,4,7,1,6,5,3,1,2,1,8,1,9,7,9,5,6,5,5,3,5,8,2,
%U A088539 0,1,0,6,6,3,9,3,6,3,7,9,2,8,1,3,9,8,9,1,3,3,0,0,4,9,9,6,2,6,0,5,2,3,4,3
%N A088539 Decimal expansion of (4K/Pi)^2 where K is the Landau-Ramanujan constant.
%D A088539 Steven R. Finch, Mathematical Constants, Encyclopedia of Mathematics and its Applications, vol. 94, Cambridge University Press, p. 100
%H A088539 W. Bosma and P. Stevenhagen, <a href="https://doi.org/10.1090/S0025-5718-96-00725-9">Density computations for real quadratic units</a>, Math. comp. 65 (1996), 1327-1337; MR 96j : 11171.
%F A088539 Equals prod(1-1/p^2) where p runs through the primes p==1 mod 4
%F A088539 A088539 * A243379 = 8 / Pi^2. - _Vaclav Kotesovec_, Apr 30 2020
%F A088539 Equals 1/A175647. - _Vaclav Kotesovec_, May 05 2020
%e A088539 0.9468064071800793342160944131097562332500695...
%t A088539 digits = 104; LandauRamanujanK = 1/Sqrt[2]*NProduct[((1-2^(-2^n)) * Zeta[2^n] / DirichletBeta[2^n])^(1/2^(n+1)), {n, 1, 24}, WorkingPrecision -> digits+5]; (4*LandauRamanujanK/Pi)^2 // RealDigits[#, 10, digits]& // First (* _Jean-François Alcover_, Mar 04 2013, updated Mar 14 2018 *)
%Y A088539 Cf. A002144, A064533, A243379, A243380. Square of A244659.
%K A088539 cons,nonn
%O A088539 0,1
%A A088539 _Benoit Cloitre_, Nov 16 2003