Pentagonal pyramidal numbers: a(n) = n^2*(n+1)/2.

Terms

a(0) =0a(1) =1a(2) =6a(3) =18a(4) =40a(5) =75a(6) =126a(7) =196a(8) =288a(9) =405a(10) =550a(11) =726a(12) =936a(13) =1183a(14) =1470a(15) =1800a(16) =2176a(17) =2601a(18) =3078a(19) =3610a(20) =4200a(21) =4851a(22) =5566a(23) =6348a(24) =7200a(25) =8125a(26) =9126a(27) =10206a(28) =11368a(29) =12615