a(n) = C(3+n, n) + C(4+n, n) + C(5+n, n) + C(6+n, n).

Terms

a(0) =4a(1) =22a(2) =74a(3) =195a(4) =441a(5) =896a(6) =1680a(7) =2958a(8) =4950a(9) =7942a(10) =12298a(11) =18473a(12) =27027a(13) =38640a(14) =54128a(15) =74460a(16) =100776a(17) =134406a(18) =176890a(19) =229999a(20) =295757a(21) =376464a(22) =474720a(23) =593450a(24) =735930a(25) =905814a(26) =1107162a(27) =1344469a(28) =1622695a(29) =1947296