Number of directed multigraphs with loops on 4 nodes with n arcs.

Terms

a(0) =1a(1) =2a(2) =11a(3) =47a(4) =198a(5) =713a(6) =2423a(7) =7388a(8) =21003a(9) =55433a(10) =137944a(11) =324659a(12) =729022a(13) =1567139a(14) =3242954a(15) =6479759a(16) =12547894a(17) =23607614a(18) =43267994a(19) =77405064a(20) =135435666a(21) =232137202a(22) =390371944a(23) =644897542a(24) =1047890293a(25) =1676518363a(26) =2643628813