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 A261509 #16 Feb 16 2025 08:33:26
%S A261509 5,4,4,4,8,7,4,4,5,6,4,8,5,3,1,7,7,3,4,0,9,9,3,6,1,0,0,4,1,3,7,6,5,0,
%T A261509 6,8,9,5,7,1,6,6,8,6,9,4,4,3,5,3,8,2,5,6,5,6,4,7,9,8,6,9,2,4,3,0,2,7,
%U A261509 9,1,0,9,4,2,3,3,3,8,4,1,6,3,9,0,3,2,5,1,6,4,4,6,8,1,7,7,8,6,3,3,0,0,9,2,9
%N A261509 Decimal expansion of -Gamma'''(1).
%H A261509 G. C. Greubel, <a href="/A261509/b261509.txt">Table of n, a(n) for n = 1..10000</a>
%H A261509 Tom M. Apostol, <a href="https://doi.org/10.1090/S0025-5718-1985-0771044-5">Formulas for higher derivatives of the Riemann zeta function</a>, Mathematics of Computation 44 (1985), p. 223-232.
%H A261509 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/GammaFunction.html">Gamma Function</a>.
%H A261509 Wikipedia, <a href="http://en.wikipedia.org/wiki/Gamma_function">Gamma function</a>.
%F A261509 From _Amiram Eldar_, Aug 06 2020: (Start)
%F A261509 Equals gamma^3 + gamma*Pi^2/2 + 2*zeta(3).
%F A261509 Equals -Integral_{x=0..oo} exp(-x)*log(x)^3 dx. (End)
%e A261509 5.4448744564853177340993610041376506895716686944353825656479...
%t A261509 RealDigits[EulerGamma^3 + (EulerGamma*Pi^2)/2 + 2*Zeta[3], 10, 120][[1]]
%o A261509 (PARI) default(realprecision, 100); Euler^3 + Euler*Pi^2/2 + 2*zeta(3) \\ _G. C. Greubel_, Aug 30 2018
%o A261509 (Magma) SetDefaultRealField(RealField(100)); R:= RealField(); L:=RiemannZeta(); EulerGamma(R)^3 + (EulerGamma(R)*Pi(R)^2)/2 + 2*Evaluate(L,3); // _G. C. Greubel_, Aug 30 2018
%Y A261509 Cf. A001620, A081855, A002117.
%K A261509 nonn,cons
%O A261509 1,1
%A A261509 _Vaclav Kotesovec_, Aug 22 2015