a(n) = ((n+1)*(2*n-1))^2.

Terms

a(0) =1a(1) =4a(2) =81a(3) =400a(4) =1225a(5) =2916a(6) =5929a(7) =10816a(8) =18225a(9) =28900a(10) =43681a(11) =63504a(12) =89401a(13) =122500a(14) =164025a(15) =215296a(16) =277729a(17) =352836a(18) =442225a(19) =547600a(20) =670761a(21) =813604a(22) =978121a(23) =1166400a(24) =1380625a(25) =1623076a(26) =1896129a(27) =2202256a(28) =2544025a(29) =2924100