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

Terms

a(0) =0a(1) =1a(2) =22a(3) =117a(4) =376a(5) =925a(6) =1926a(7) =3577a(8) =6112a(9) =9801a(10) =14950a(11) =21901a(12) =31032a(13) =42757a(14) =57526a(15) =75825a(16) =98176a(17) =125137a(18) =157302a(19) =195301a(20) =239800a(21) =291501a(22) =351142a(23) =419497a(24) =497376a(25) =585625a(26) =685126a(27) =796797a(28) =921592a(29) =1060501