Octahedral numbers: a(n) = n*(2*n^2 + 1)/3.

Terms

a(0) =0a(1) =1a(2) =6a(3) =19a(4) =44a(5) =85a(6) =146a(7) =231a(8) =344a(9) =489a(10) =670a(11) =891a(12) =1156a(13) =1469a(14) =1834a(15) =2255a(16) =2736a(17) =3281a(18) =3894a(19) =4579a(20) =5340a(21) =6181a(22) =7106a(23) =8119a(24) =9224a(25) =10425a(26) =11726a(27) =13131a(28) =14644a(29) =16269