54916854316domain: NAppears in sequencesa(n) = smallest number m which can be obtained in n ways by subtracting twice a triangular number from a perfect square.at n=22A078714Expansion of -2*x*(-8-12*x+9*x^2) / ( (x-1)*(3*x-1)*(3*x+1)*(1+x) ).at n=21A120468a(n) = (7*9^n + 1)/4.at n=11A199565