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 A338858 #50 Jan 15 2021 20:32:46
%S A338858 2,1,0,9,3,2,9,9,2,7,6,2,0,0,4,9,1,8,9,3,9,1,9,5,2,8,6,4,0,2,1,5,6,5,
%T A338858 7,6,7,5,9,2,1,1,1,5,3,8,5,1,7,3,2,6,1,1,0,1,9,3,7,8,4,7,9,5,0,1,8,8,
%U A338858 6,4,2,0,7,6,8,4,7,2,6,6,2,1,6,0,2,0,8,8,8,6,3,9,3,6,0,0,2,1,0,6,6,4,1,9,8
%N A338858 Decimal expansion of Sum_{k>=0} (zeta(4*k+3)-1).
%C A338858 For additional comments and generalization see A339604.
%F A338858 Equals Sum_{k>=2} k/(k^4-1).
%F A338858 Equals -1/8 + gamma/2 + Re(Psi(i))/2, where Psi is the digamma function, gamma is the Euler-Mascheroni constant (see A001620), and i=sqrt(-1).
%F A338858 Equals -1/8 + Re(H(I))/2, where H is the harmonic number function.
%e A338858 0.2109329927620049189391952864...
%t A338858 RealDigits[N[Re[Sum[Zeta[4 n + 3] - 1, {n, 0, Infinity}]], 105]][[1]]
%o A338858 (PARI) suminf(k=0, zeta(4*k+3)-1) \\ _Michel Marcus_, Dec 24 2020
%Y A338858 Cf. A256919 (4*k), A339097 (4*k+1), A339083 (4k+2).
%Y A338858 Cf. A024006, A338815, A339135, A339529, A339530, A339604, A339605, A339606.
%K A338858 nonn,cons
%O A338858 0,1
%A A338858 _Artur Jasinski_, Dec 24 2020