a(n) = n*(n + 1)*(3*n^2 + 3*n - 2)/8.

Terms

a(0) =0a(1) =1a(2) =12a(3) =51a(4) =145a(5) =330a(6) =651a(7) =1162a(8) =1926a(9) =3015a(10) =4510a(11) =6501a(12) =9087a(13) =12376a(14) =16485a(15) =21540a(16) =27676a(17) =35037a(18) =43776a(19) =54055a(20) =66045a(21) =79926a(22) =95887a(23) =114126a(24) =134850a(25) =158275a(26) =184626a(27) =214137a(28) =247051a(29) =283620