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A361405
Number of graphs with loops on 2n unlabeled vertices with n loops.
2
1, 2, 28, 1408, 580656, 2658827456, 146702084635392, 98485306566812364032, 820443196111261227164076544, 86804253216450161933010414314819072, 119212631345634236227720012129209606659383296, 2166023316743980619769969171366251471253351621687457792
OFFSET
0,2
COMMENTS
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.
LINKS
FORMULA
a(n) = A361404(2*n, n).
PROG
(PARI) a(n) = row(2*n)[n+1] \\ row(n) defined in A361404.
CROSSREFS
Central coefficients of A361404.
Cf. A007139.
Sequence in context: A324077 A071220 A063794 * A331839 A238817 A202942
KEYWORD
nonn
AUTHOR
Andrew Howroyd, Mar 11 2023
STATUS
approved