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 A340809 #29 Aug 25 2021 21:25:36
%S A340809 1,0,0,0,0,0,9,2,2,6,1,5,8,1,0,2,5,7,5,1,4,1,6,8,8,0,4,1,4,3,8,4,7,1,
%T A340809 5,4,7,5,1,1,0,1,0,4,0,4,7,9,5,3,7,1,9,6,9,8,8,5,0,4,3,5,5,0,0,7,5,8,
%U A340809 3,4,2,2,9,7,8,6,8,4,8,4,7,9,5,5,1,5,3,2,0,9,8,4,2,4,8,7,4,4,6,6,5,2,9,9,6
%N A340809 Decimal expansion of Product_{primes p == 4 (mod 5)} 1/(1-p^(-4)).
%C A340809 Equals also the same product over the primes p==9 (mod 10).
%H A340809 Vaclav Kotesovec, <a href="/A340809/b340809.txt">Table of n, a(n) for n = 1..500</a>
%H A340809 R. J. Mathar, <a href="https://arxiv.org/abs/1008.2547">Table of Dirichlet L-series and prime zeta modulo functions for small moduli</a>, arXiv:1008.2547 [math.NT], 2010-2015, Zeta_{m=5,n=4}(s=4).
%F A340809 Equals A340127 ^2/A340628
%F A340809 Equals Sum_{k>=1} 1/A004618(k)^4. - _Amiram Eldar_, Jan 24 2021
%e A340809 1.0000092261581025751416880414384715475110104...
%Y A340809 Cf. A004618, A030433, A340127 (s=2), A340628, A340808, A340926, A340927.
%K A340809 nonn,cons
%O A340809 1,7
%A A340809 _R. J. Mathar_, Jan 22 2021
%E A340809 More digits from _Vaclav Kotesovec_, Jan 22 2021