Squares of tribonacci numbers A000213.

Terms

a(0) =1a(1) =1a(2) =1a(3) =9a(4) =25a(5) =81a(6) =289a(7) =961a(8) =3249a(9) =11025a(10) =37249a(11) =126025a(12) =426409a(13) =1442401a(14) =4879681a(15) =16507969a(16) =55845729a(17) =188925025a(18) =639128961a(19) =2162157001a(20) =7314525625a(21) =24744863025a(22) =83711270241a(23) =283193201281a(24) =958035736849