OFFSET
2,2
LINKS
Eric Weisstein's World of Mathematics, Gram Point
EXAMPLE
17.8455995...
MATHEMATICA
First[ RealDigits[t /. FindRoot[ RiemannSiegelTheta[t] == 0, {t, 17}, WorkingPrecision -> 120], 10, 102]] (* Jean-François Alcover, Jun 07 2012 *)
PROG
(PARI) g0(n)=2*Pi*exp(1+lambertw((8*n+1)/exp(1)/8)) \\ approximate location of gram(n)
th(t)=arg(gamma(1/4+I*t/2))-log(Pi)*t/2 \\ theta, but off by some integer multiple of 2*Pi
thapprox(t)=log(t/2/Pi)*t/2-t/2-Pi/8+1/48/t-1/5760/t^3
RStheta(t)=my(T=th(t)); (thapprox(t)-T)\/(2*Pi)*2*Pi+T
gram(n)=my(G=g0(n), k=n*Pi); solve(x=G-.003, G+1e-8, RStheta(x)-k)
gram(0) \\ Charles R Greathouse IV, Jan 22 2022
(PARI) solve(t=17.8, 18, 4*Pi+arg(gamma(1/4+I*t/2))-log(Pi)*t/2) \\ Charles R Greathouse IV, Mar 27 2023
CROSSREFS
KEYWORD
nonn,cons
AUTHOR
Eric W. Weisstein, Jan 02 2006
STATUS
approved