A055969 - OEIS

%I #11 Sep 12 2019 09:40:39

%S 0,1,6,104,4736,770112,440994608,896679244544,6513978322585408,

%T 170630215971902124288,16261454692523251085611648,

%U 5683372715412699486531047331840,7334542846356464931239079919515090432,35157828307617499760690834338506768579289088

%N Number of unlabeled digraphs with n nodes and an odd number of arcs.

%H Andrew Howroyd, <a href="/A055969/b055969.txt">Table of n, a(n) for n = 1..50</a>

%F a(n) = (A000273(n)-A003086(n))/2.

%t A000273 = Cases[Import["https://oeis.org/A000273/b000273.txt", "Table"], {_, _}][[All, 2]];

%t A003086 = Cases[Import["https://oeis.org/A003086/b003086.txt", "Table"], {_, _}][[All, 2]];

%t a[n_] := (A000273[[n + 1]] - A003086[[n]])/2;

%t Array[a, 50] (* _Jean-François Alcover_, Sep 12 2019, after _Andrew Howroyd_ *)

%Y Cf. A054928, A007869, A054960.

%K easy,nonn

%O 1,3

%A _Vladeta Jovovic_, Jul 19 2000

%E Terms a(14) and beyond from _Andrew Howroyd_, Sep 17 2018