a(n) = 2*a(n-1)^2 - 1, starting a(0) = 2.A002812a(n) = 2*a(n-1)^2 - 1, starting a(0) = 2.Terms a(0) =2a(1) =7a(2) =97a(3) =18817a(4) =708158977External referencesoeis: A002812