Squares of odd pentagonal pyramidal numbers.

Terms

a(0) =1a(1) =5625a(2) =164025a(3) =1399489a(4) =6765201a(5) =23532201a(6) =66015625a(7) =159138225a(8) =342731169a(9) =676572121a(10) =1246160601a(11) =2169230625a(12) =3603000625a(13) =5752160649a(14) =8877596841a(15) =13305853201a(16) =19439330625a(17) =27767223225a(18) =38877191929a(19) =53467775361