Odd 9-gonal (or enneagonal) numbers.

Terms

a(0) =1a(1) =9a(2) =75a(3) =111a(4) =261a(5) =325a(6) =559a(7) =651a(8) =969a(9) =1089a(10) =1491a(11) =1639a(12) =2125a(13) =2301a(14) =2871a(15) =3075a(16) =3729a(17) =3961a(18) =4699a(19) =4959a(20) =5781a(21) =6069a(22) =6975a(23) =7291a(24) =8281a(25) =8625a(26) =9699a(27) =10071a(28) =11229a(29) =11629