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 A256843 #19 Jan 07 2024 01:51:45
%S A256843 0,7,3,2,0,7,3,7,5,7,0,6,1,5,9,5,9,3,6,6,9,0,3,1,8,5,9,9,0,7,5,2,9,1,
%T A256843 3,9,0,7,4,6,2,3,8,3,0,2,6,8,3,0,9,3,4,5,6,2,9,3,9,0,6,4,4,6,6,9,8,5,
%U A256843 1,0,9,4,2,7,4,5,9,7,4,0,4,1,7,7,2,3,0,8,1,5,5,3,0,8,6,0,9,0,3,1,6,0,1,6,8,4
%N A256843 Decimal expansion of the generalized Euler constant gamma(2,3).
%H A256843 G. C. Greubel, <a href="/A256843/b256843.txt">Table of n, a(n) for n = 0..10000</a>
%H A256843 D. H. Lehmer, <a href="http://matwbn.icm.edu.pl/ksiazki/aa/aa27/aa27121.pdf">Euler constants for arithmetic progressions</a>, Acta Arith. 27 (1975), p. 134.
%F A256843 Equals EulerGamma/3 - Pi/(6*sqrt(3)) + log(3)/6.
%F A256843 Equals -(psi(2/3) + log(3))/3 = (A200064 - A002391)/3. - _Amiram Eldar_, Jan 07 2024
%e A256843 0.07320737570615959366903185990752913907462383026830934562939...
%t A256843 Join[{0}, RealDigits[-Log[3]/3 - PolyGamma[2/3]/3, 10, 105] // First]
%o A256843 (PARI) default(realprecision, 100); Euler/3 - Pi/(6*sqrt(3)) + log(3)/6 \\ _G. C. Greubel_, Aug 28 2018
%o A256843 (Magma) SetDefaultRealField(RealField(100)); R:= RealField(); EulerGamma(R)/3 - Pi(R)/(6*Sqrt(3)) + Log(3)/6; // _G. C. Greubel_, Aug 28 2018
%Y A256843 Cf. A001620 (gamma(1,1) = EulerGamma), A002391, A200064.
%Y A256843 Primitive ruler-and-compass constructible gamma(r,k): A228725 (1,2), A256425 (1,3), A256778 (1,4), A256779 (1,5), A256780 (2,5), A256781 (1,8), A256782 (3,8), A256783 (1,12), A256784 (5,12).
%Y A256843 Other gamma(r,k) (1 <= r <= k <= 5): A239097 (2,2), A256843 (2,3), A256844 (3,3), A256845 (2,4), A256846 (3,4), A256847 (4,4), A256848 (3,5), A256849 (4,5), A256850 (5,5).
%K A256843 nonn,cons,easy
%O A256843 0,2
%A A256843 _Jean-François Alcover_, Apr 11 2015