a(n) = n*(n+1)*(3*n^2+n-1)/6.

Terms

a(0) =0a(1) =1a(2) =13a(3) =58a(4) =170a(5) =395a(6) =791a(7) =1428a(8) =2388a(9) =3765a(10) =5665a(11) =8206a(12) =11518a(13) =15743a(14) =21035a(15) =27560a(16) =35496a(17) =45033a(18) =56373a(19) =69730a(20) =85330a(21) =103411a(22) =124223a(23) =148028a(24) =175100a(25) =205725a(26) =240201a(27) =278838a(28) =321958a(29) =369895