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A289896 Number of (undirected) cycles in the n-triangular honeycomb rook graph. 0
0, 0, 1, 8, 45, 242, 1414, 9432, 72246, 628260, 6116319, 65856928, 776628203, 9950798214, 137612550620, 2042588039056, 32384583304092, 546155914771464, 9761655297881037, 184309987662192600, 3665514979650544153, 76586509823743735706, 1677182881414143407490 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

Table of n, a(n) for n=1..23.

Eric Weisstein's World of Mathematics, Graph Cycle

FORMULA

a(n) = sum(k=1..n,A002807(k)).

MATHEMATICA

Table[Sum[Binomial[k, l] (l - 1)!, {k, n}, {l, 3, k}]/2, {n, 20}]

Table[Sum[k (2 HypergeometricPFQ[{1, 1, 1 - k}, {2}, -1] - k - 1)/4, {k, n}], {n, 20}]

CROSSREFS

Cf. A002807 (cycles in the complete graph).

Sequence in context: A163003 A055422 A204618 * A006887 A009369 A120044

Adjacent sequences:  A289893 A289894 A289895 * A289897 A289898 A289899

KEYWORD

nonn

AUTHOR

Eric W. Weisstein, Jul 14 2017

STATUS

approved

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Last modified September 26 14:12 EDT 2017. Contains 292529 sequences.