a(n) = n-th odd nonprime * n-th odd number.

Terms

a(0) =1a(1) =27a(2) =75a(3) =147a(4) =225a(5) =297a(6) =429a(7) =525a(8) =663a(9) =855a(10) =1029a(11) =1173a(12) =1375a(13) =1539a(14) =1827a(15) =2015a(16) =2277a(17) =2625a(18) =2849a(19) =3159a(20) =3485a(21) =3741a(22) =4095a(23) =4371a(24) =4655a(25) =5049a(26) =5565a(27) =6105a(28) =6555a(29) =6903