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A340665 Decimal expansion of Product_{primes p == 3 (mod 5)} p^2/(p^2-1).

%I A340665 #31 Jan 27 2021 05:19:58
%S A340665 1,1,3,5,7,6,4,8,7,8,6,6,8,9,2,1,6,2,6,8,6,8,6,4,3,0,0,9,4,7,2,0,8,2,
%T A340665 2,8,9,5,1,1,9,3,6,4,1,3,0,0,5,4,6,8,7,4,4,1,6,4,9,9,7,4,3,0,1,6,3,4,
%U A340665 0,6,4,3,1,6,7,2,0,0,2,9,6,6,0,9,9,0,0,6,8,4,6,0,3,7,1,9,8,3,9,6,8,5,1,9
%N A340665 Decimal expansion of Product_{primes p == 3 (mod 5)} p^2/(p^2-1).
%H A340665 Vaclav Kotesovec, <a href="/A340665/b340665.txt">Table of n, a(n) for n = 1..501</a>
%H A340665 R. J. Mathar, <a href="https://arxiv.org/abs/1008.2547">Table of Dirichlet L-series and prime zeta modulo functions...</a>, arXiv:1008.2547 Zeta_{m=5,n=3}(s=2).
%H A340665 For links see A340628.
%F A340665 Equals Sum_{k>=1} 1/A004617(k)^2. - _Amiram Eldar_, Jan 24 2021
%e A340665 1.135764878668921626868643009472082289511936413...
%t A340665 (* Using Vaclav Kotesovec's function Z from A301430. *)
%t A340665 $MaxExtraPrecision = 100; digits = 50; (* Adjust as needed. *)
%t A340665 digitize[c_] := RealDigits[Chop[N[c, digits+10]], 10, digits][[1]];
%t A340665 digitize[Z[5, 3, 2]]
%Y A340665 Cf. A004617, A175646, A175647, A248930, A248938, A301429, A333240, A334826, A335963, A340576, A340577, A340578, A340628, A340628, A340004, A340127.
%K A340665 nonn,cons
%O A340665 1,3
%A A340665 _Artur Jasinski_, Jan 15 2021