1) a(n) = (2^n*sqrt((5762440*sqrt(20753571721*u(n)^198-13553934642*u(n)^99+4518487526)-830142868840*u(n)^99+271078692840)^(1/3)- (8584820*11^(2/3))/(5762440*sqrt(20753571721*u(n)^198-13553934642*u(n)^99+4518487526)-830142868840*u(n)^99+271078692840)^(1/3)+2950*11^(1/3)))/(11^(1/6)*sqrt(144061)) ; 2) (2^n*sqrt( (-306267858538119720*u(n)^(1/99)+1990548992520*sqrt(23673207321*u(n)^(2/99)-47605249842*u(n)^(1/99)+23933777126)+307942175442951720)^(1/3)- 15965632980/(-306267858538119720*u(n)^(1/99)+1990548992520*sqrt(23673207321*u(n)^(2/99)-47605249842*u(n)^(1/99)+23933777126)+307942175442951720)^(1/3)-64350))/( sqrt(51287)) ; 3) a(n)=(2^n*sqrt(- (16483125780*u(n)^(1/297))/(-328586152174659720*u(n)^(1/99)+2067396673320*sqrt(25262068046*u(n)^(2/99)-50796633642*u(n)^(1/99)+25536359601)+330372055793209320)^(1/3)+ (-328586152174659720*u(n)^(1/99)+2067396673320*sqrt(25262068046*u(n)^(2/99)-50796633642*u(n)^(1/99)+25536359601)+330372055793209320)^(1/3)/u(n)^(1/297)-66330))/( sqrt(53267)); for each of them u(n+1)=sqrt(2*u(n)+2)/2 u(2) = sqrt(2)/2 n ---------- infinity a(n) ------- Pi