a(n) = n*(n+1)*(n+2)*(n+3)*(1+3*n+n^2)/120.

Terms

a(0) =1a(1) =11a(2) =57a(3) =203a(4) =574a(5) =1386a(6) =2982a(7) =5874a(8) =10791a(9) =18733a(10) =31031a(11) =49413a(12) =76076a(13) =113764a(14) =165852a(15) =236436a(16) =330429a(17) =453663a(18) =612997a(19) =816431a(20) =1073226a(21) =1394030a(22) =1791010a(23) =2277990a(24) =2870595a(25) =3586401a(26) =4445091a(27) =5468617a(28) =6681368a(29) =8110344