a(n) = (n+1)(n+2)(n+3)(2n+3)(10n^2 + 27n + 20)/360.

Terms

a(0) =1a(1) =19a(2) =133a(3) =573a(4) =1848a(5) =4914a(6) =11382a(7) =23766a(8) =45771a(9) =82621a(10) =141427a(11) =231595a(12) =365274a(13) =557844a(14) =828444a(15) =1200540a(16) =1702533a(17) =2368407a(18) =3238417a(19) =4359817a(20) =5787628a(21) =7585446a(22) =9826290a(23) =12593490a(24) =15981615a(25) =20097441a(26) =25060959a(27) =31006423a(28) =38083438a(29) =46458088