a(n) = C(n+3,4) + 3*C(n+1,3) + 5*C(n-1,2) + 7*n - 15.

Terms

a(0) =7a(1) =38a(2) =93a(3) =180a(4) =308a(5) =487a(6) =728a(7) =1043a(8) =1445a(9) =1948a(10) =2567a(11) =3318a(12) =4218a(13) =5285a(14) =6538a(15) =7997a(16) =9683a(17) =11618a(18) =13825a(19) =16328a(20) =19152a(21) =22323a(22) =25868a(23) =29815a(24) =34193a(25) =39032a(26) =44363a(27) =50218a(28) =56630a(29) =63633