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Number of unlabeled digraphs with loops (relations) on n nodes and with an odd number of arcs.
2

%I #8 Apr 19 2020 18:24:01

%S 0,1,4,52,1504,145984,48461696,56141454464,229148544420864,

%T 3333310786076963968,174695272746603272722432,

%U 33301710992539090379269318144,23278728241293494481773139193036800,60084295633556503802059558812644803074048,576025077880237078776946485247979728479746359296

%N Number of unlabeled digraphs with loops (relations) on n nodes and with an odd number of arcs.

%H Andrew Howroyd, <a href="/A055974/b055974.txt">Table of n, a(n) for n = 0..50</a>

%F a(2*n) = (A000595(2*n) - A047832(n))/2; a(2*n+1) = A000595(2*n+1)/2.

%F a(n) = (A000595(n) - A000171(2*n+1))/2.

%Y Cf. A000171, A000595, A047832, A054960, A055973.

%K easy,nonn

%O 0,3

%A _Vladeta Jovovic_, Jul 19 2000

%E a(0)=0 prepended and terms a(13) and beyond from _Andrew Howroyd_, Apr 19 2020