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 A257818 Decimal expansion of the imaginary part of li(i), i being the imaginary unit. 4
 2, 9, 4, 1, 5, 5, 8, 4, 9, 4, 9, 4, 9, 3, 8, 5, 0, 9, 9, 3, 0, 0, 9, 9, 9, 9, 8, 0, 0, 2, 1, 3, 2, 6, 7, 7, 2, 0, 8, 9, 4, 4, 6, 0, 3, 5, 2, 5, 1, 9, 2, 1, 5, 9, 0, 1, 2, 2, 7, 0, 4, 4, 3, 9, 2, 8, 3, 9, 4, 3, 5, 6, 4, 2, 1, 1, 0, 6, 0, 7, 2, 5, 0, 3, 4, 0, 8, 2, 6, 5, 3, 4, 8, 4, 9, 5, 9, 0, 9, 4, 9, 3, 4, 6, 7 (list; constant; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS li(x) is the logarithmic integral function, extended to the whole complex plane. The corresponding real part is in A257817. LINKS Stanislav Sykora, Table of n, a(n) for n = 1..2000 Eric Weisstein's World of Mathematics, Logarithmic Integral Wikipedia, Logarithmic integral function FORMULA Equals (Pi/2)*(1+Sum_{k>=0}((-1)^k*(Pi/2)^(2*k)/(2*k+1)!/(2*k+1))). EXAMPLE 2.941558494949385099300999980021326772089446035251921590122704439... MAPLE evalf(Im(Li(I)), 120); # Vaclav Kotesovec, May 10 2015 evalf(Pi/2*(1+Sum(((-1)^k*(Pi/2)^(2*k)/(2*k+1)!/(2*k+1)), k=0..infinity)), 120); # Vaclav Kotesovec, May 10 2015 MATHEMATICA RealDigits[Im[LogIntegral[I]], 10, 120][[1]] (* Vaclav Kotesovec, May 10 2015 *) PROG (PARI) li(z) = {my(c=z+0.0*I); \\ If z is real, convert it to complex   if(imag(c)<0, return(-Pi*I-eint1(-log(c))),   return(+Pi*I-eint1(-log(c)))); }   a=imag(li(I)) CROSSREFS Cf. A019669, A257817. Sequence in context: A309929 A161934 A021038 * A195485 A011067 A135008 Adjacent sequences:  A257815 A257816 A257817 * A257819 A257820 A257821 KEYWORD nonn,cons AUTHOR Stanislav Sykora, May 10 2015 STATUS approved

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Last modified October 14 01:36 EDT 2019. Contains 327994 sequences. (Running on oeis4.)