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%I #8 Mar 11 2023 19:46:27
%S 1,2,28,1408,580656,2658827456,146702084635392,98485306566812364032,
%T 820443196111261227164076544,86804253216450161933010414314819072,
%U 119212631345634236227720012129209606659383296,2166023316743980619769969171366251471253351621687457792
%N Number of graphs with loops on 2n unlabeled vertices with n loops.
%C a(n) is the number of bicolored graphs on 2n unlabeled nodes with an equal number of each color. Adjacent vertices may have the same color.
%H Andrew Howroyd, <a href="/A361405/b361405.txt">Table of n, a(n) for n = 0..25</a>
%F a(n) = A361404(2*n, n).
%o (PARI) a(n) = row(2*n)[n+1] \\ row(n) defined in A361404.
%Y Central coefficients of A361404.
%Y Cf. A007139.
%K nonn
%O 0,2
%A _Andrew Howroyd_, Mar 11 2023
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