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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 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.