a(n) = n*(16*n^2 + 3*n - 13)/6.

Terms

a(0) =0a(1) =1a(2) =19a(3) =70a(4) =170a(5) =335a(6) =581a(7) =924a(8) =1380a(9) =1965a(10) =2695a(11) =3586a(12) =4654a(13) =5915a(14) =7385a(15) =9080a(16) =11016a(17) =13209a(18) =15675a(19) =18430a(20) =21490a(21) =24871a(22) =28589a(23) =32660a(24) =37100a(25) =41925a(26) =47151a(27) =52794a(28) =58870a(29) =65395