163760domain: NAppears in sequencesa(n) = OrdinaryUnitarySigma(a(n-1)).at n=15A126850Nonnegative values x of solutions (x, y) to the Diophantine equation x^2+(x+409)^2 = y^2.at n=11A129641Number of n X 3 0..1 arrays avoiding 0 0 0 and 0 0 1 horizontally and 0 0 0 and 1 1 1 vertically.at n=9A207840