Octagonal pyramidal numbers: a(n) = n*(n+1)*(2*n-1)/2.

Terms

a(0) =1a(1) =9a(2) =30a(3) =70a(4) =135a(5) =231a(6) =364a(7) =540a(8) =765a(9) =1045a(10) =1386a(11) =1794a(12) =2275a(13) =2835a(14) =3480a(15) =4216a(16) =5049a(17) =5985a(18) =7030a(19) =8190a(20) =9471a(21) =10879a(22) =12420a(23) =14100a(24) =15925a(25) =17901a(26) =20034a(27) =22330a(28) =24795a(29) =27435