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 A242712 #13 Feb 16 2025 08:33:22 %S A242712 1,9,4,8,4,5,4,7,8,8,9,5,8,8,3,5,6,0,6,7,0,3,1,0,2,4,6,6,8,8,6,5,7,5, %T A242712 5,5,8,3,0,0,7,5,8,1,7,2,0,8,8,3,4,5,8,3,8,6,1,7,8,1,6,5,3,9,0,0,8,5, %U A242712 9,5,9,1,3,5,0,4,1,4,2,2,0,5,9,6,4,3,4,5,9,5,5,3,3,9,4,5,7,8,1,4 %N A242712 Decimal expansion of C_4, a constant related to sharp inequalities for the product of 4 polynomials, which was introduced by David Boyd. %D A242712 Steven R. Finch, Mathematical Constants, Cambridge, 2003, Section 3.10 p. 233. %H A242712 David W. Boyd, <a href="https://citeseerx.ist.psu.edu/pdf/522373ad9d2ff1a77a4054e6c28d8da3df682e5d">Sharp inequalities for the product of polynomials</a> %H A242712 Eric Weisstein's MathWorld, <a href="https://mathworld.wolfram.com/ClausensIntegral.html">Clausen's Integral</a> %F A242712 exp(4/Pi*Clausen2(Pi - Pi/4)), where Clausen2 is Clausen's Integral. %e A242712 1.9484547889588356067031024668865755583... %t A242712 Clausen2[x_] := Im[PolyLog[2, Exp[x*I]]]; c[m_] := Exp[m/Pi*Clausen2[Pi - Pi/m]]; RealDigits[c[4], 10, 100] // First %o A242712 (PARI) exp(4*imag(polylog(2, exp(3*I*Pi/4)))/Pi) \\ _Charles R Greathouse IV_, Jul 15 2014 %Y A242712 Cf. A130834 (C_2), A242711 (C_3), A242713 (C_5), A242714 (C_6). %K A242712 nonn,cons %O A242712 1,2 %A A242712 _Jean-François Alcover_, May 21 2014