Tetrahedral (or triangular pyramidal) numbers: a(n) = C(n+2,3) = n*(n+1)*(n+2)/6.

Terms

a(0) =0a(1) =1a(2) =4a(3) =10a(4) =20a(5) =35a(6) =56a(7) =84a(8) =120a(9) =165a(10) =220a(11) =286a(12) =364a(13) =455a(14) =560a(15) =680a(16) =816a(17) =969a(18) =1140a(19) =1330a(20) =1540a(21) =1771a(22) =2024a(23) =2300a(24) =2600a(25) =2925a(26) =3276a(27) =3654a(28) =4060a(29) =4495