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 A290940 Number of 6-cycles in the n-triangular graph. 3
 0, 0, 16, 920, 7800, 36260, 122080, 334656, 794640, 1696200, 3334320, 6137560, 10706696, 17859660, 28683200, 44591680, 67393440, 99365136, 143334480, 202771800, 281890840, 385759220, 520418976, 693017600, 911950000, 1187011800, 1529564400, 1952712216, 2471492520 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,3 LINKS Eric Weisstein's World of Mathematics, Graph Cycle Eric Weisstein's World of Mathematics, Johnson Graph Eric Weisstein's World of Mathematics, Triangular Graph Index entries for linear recurrences with constant coefficients, signature (8, -28, 56, -70, 56, -28, 8, -1). FORMULA a(n) = 2*binomial(n, 4) (n^3 + 27*n^2 - 220*n + 392). a(n) = 8*a(n-1) - 28*a(n-2) + 56*a(n-3) - 70*a(n-4) + 56*a(n-5) - 28*a(n-6) + 8*a(n-7) - a(n-8). G.f.: -((4*x^2 (-4*x^2 - 198*x^3 - 222*x^4 + 319*x^5))/(-1 + x)^8). MATHEMATICA Table[2 Binomial[n, 4] (n^3 + 27 n^2 - 220 n + 392), {n, 2, 20}] LinearRecurrence[{8, -28, 56, -70, 56, -28, 8, -1}, {0, 0, 16, 920, 7800, 36260, 122080, 334656}, 20] CoefficientList[Series[-((4 (-4 x^2 - 198 x^3 - 222 x^4 + 319 x^5))/(-1 + x)^8), {x, 0, 20}], x] CROSSREFS Cf. A002417 (3-cycles), A151974 (4-cycles), A290939 (5-cycles). Sequence in context: A289707 A006089 A260620 * A173953 A211105 A276637 Adjacent sequences:  A290937 A290938 A290939 * A290941 A290942 A290943 KEYWORD nonn,easy AUTHOR Eric W. Weisstein, Aug 14 2017 STATUS approved

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Last modified October 15 14:07 EDT 2018. Contains 316236 sequences. (Running on oeis4.)