a(n) = (n^3 + 18*n^2 + 17*n + 6)/6.

Terms

a(0) =1a(1) =7a(2) =20a(3) =41a(4) =71a(5) =111a(6) =162a(7) =225a(8) =301a(9) =391a(10) =496a(11) =617a(12) =755a(13) =911a(14) =1086a(15) =1281a(16) =1497a(17) =1735a(18) =1996a(19) =2281a(20) =2591a(21) =2927a(22) =3290a(23) =3681a(24) =4101a(25) =4551a(26) =5032a(27) =5545a(28) =6091a(29) =6671