(1/2)*(n^2+n+2)*(n^2+3*n+1).

Terms

a(0) =1a(1) =10a(2) =44a(3) =133a(4) =319a(5) =656a(6) =1210a(7) =2059a(8) =3293a(9) =5014a(10) =7336a(11) =10385a(12) =14299a(13) =19228a(14) =25334a(15) =32791a(16) =41785a(17) =52514a(18) =65188a(19) =80029a(20) =97271a(21) =117160a(22) =139954a(23) =165923a(24) =195349a(25) =228526a(26) =265760a(27) =307369a(28) =353683a(29) =405044