Even 9-gonal (or enneagonal) numbers.

Terms

a(0) =0a(1) =24a(2) =46a(3) =154a(4) =204a(5) =396a(6) =474a(7) =750a(8) =856a(9) =1216a(10) =1350a(11) =1794a(12) =1956a(13) =2484a(14) =2674a(15) =3286a(16) =3504a(17) =4200a(18) =4446a(19) =5226a(20) =5500a(21) =6364a(22) =6666a(23) =7614a(24) =7944a(25) =8976a(26) =9334a(27) =10450a(28) =10836a(29) =12036