Even tetrahedral numbers.

Terms

a(0) =0a(1) =4a(2) =10a(3) =20a(4) =56a(5) =84a(6) =120a(7) =220a(8) =286a(9) =364a(10) =560a(11) =680a(12) =816a(13) =1140a(14) =1330a(15) =1540a(16) =2024a(17) =2300a(18) =2600a(19) =3276a(20) =3654a(21) =4060a(22) =4960a(23) =5456a(24) =5984a(25) =7140a(26) =7770a(27) =8436a(28) =9880a(29) =10660