Lower level digraph derived from a voltage graph.

Terms

a(0) =0a(1) =1a(2) =0a(3) =0a(4) =1a(5) =3a(6) =3a(7) =2a(8) =6a(9) =15a(10) =21a(11) =24a(12) =42a(13) =86a(14) =138a(15) =192a(16) =305a(17) =546a(18) =906a(19) =1381a(20) =2175a(21) =3651a(22) =6042a(23) =9582a(24) =15225a(25) =24901a(26) =40836a(27) =65748a(28) =105364a(29) =170796