4 times 9-gonal numbers: a(n) = 2*n*(7*n-5).

Terms

a(0) =0a(1) =4a(2) =36a(3) =96a(4) =184a(5) =300a(6) =444a(7) =616a(8) =816a(9) =1044a(10) =1300a(11) =1584a(12) =1896a(13) =2236a(14) =2604a(15) =3000a(16) =3424a(17) =3876a(18) =4356a(19) =4864a(20) =5400a(21) =5964a(22) =6556a(23) =7176a(24) =7824a(25) =8500a(26) =9204a(27) =9936a(28) =10696a(29) =11484