a(n) = 7*n*(2*n + 1).

Terms

a(0) =0a(1) =21a(2) =70a(3) =147a(4) =252a(5) =385a(6) =546a(7) =735a(8) =952a(9) =1197a(10) =1470a(11) =1771a(12) =2100a(13) =2457a(14) =2842a(15) =3255a(16) =3696a(17) =4165a(18) =4662a(19) =5187a(20) =5740a(21) =6321a(22) =6930a(23) =7567a(24) =8232a(25) =8925a(26) =9646a(27) =10395a(28) =11172a(29) =11977