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 A301774 Number of chordless cycles in the (2n+1)-prism graph. 1
 2, 12, 30, 74, 200, 522, 1362, 3572, 9350, 24474, 64080, 167762, 439202, 1149852, 3010350, 7881194, 20633240, 54018522, 141422322, 370248452, 969323030, 2537720634, 6643838880, 17393796002, 45537549122, 119218851372, 312119004990, 817138163594, 2139295485800 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Sequence extended to a(1) using the formula/recurrence (actual count for the 3-prism is 0, which reproduces A301775). LINKS Eric Weisstein's World of Mathematics, Chordless Cycle Eric Weisstein's World of Mathematics, Prism Graph Index entries for linear recurrences with constant coefficients, signature (2, 1, 2, -1). FORMULA a(n) = lucasl(2*n + 1) + 2*cos((2*n + 1)*Pi/3). a(n) = 2*a(n-1) + a(n-2) + 2*a(n-3) - a(n-4). G.f.: -2*(-1 - 4*x - 2*x^2 + x^3)/(1 - 2*x - x^2 - 2*x^3 + x^4). MATHEMATICA Table[LucasL[2 n + 1] + 2 Cos[(2 n + 1) Pi/3], {n, 20}] LinearRecurrence[{2, 1, 2, -1}, {2, 12, 30, 74}, 20] CoefficientList[Series[-2 (-1 - 4 x - 2 x^2 + x^3)/(1 - 2 x - x^2 - 2 x^3 + x^4), {x, 0, 20}], x] CROSSREFS Cf. A301775. Sequence in context: A127118 A259127 A296257 * A286230 A083175 A019258 Adjacent sequences:  A301771 A301772 A301773 * A301775 A301776 A301777 KEYWORD nonn AUTHOR Eric W. Weisstein, Mar 26 2018 STATUS approved

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Last modified August 19 08:17 EDT 2019. Contains 326115 sequences. (Running on oeis4.)