Divisible exactly by the square of a prime.

Terms

a(0) =4a(1) =9a(2) =12a(3) =18a(4) =20a(5) =25a(6) =28a(7) =36a(8) =44a(9) =45a(10) =49a(11) =50a(12) =52a(13) =60a(14) =63a(15) =68a(16) =72a(17) =75a(18) =76a(19) =84a(20) =90a(21) =92a(22) =98a(23) =99a(24) =100a(25) =108a(26) =116a(27) =117a(28) =121a(29) =124