x such that x^2 - 21*y^2 = 1.A114049x such that x^2 - 21*y^2 = 1.Terms a(0) =1a(1) =55a(2) =6049a(3) =665335a(4) =73180801a(5) =8049222775a(6) =885341324449External referencesoeis: A114049