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 A290707 a(n) = 2^(n+1) + n^2 - 1. 2
 1, 4, 11, 24, 47, 88, 163, 304, 575, 1104, 2147, 4216, 8335, 16552, 32963, 65760, 131327, 262432, 524611, 1048936, 2097551, 4194744, 8389091, 16777744, 33555007, 67109488, 134218403, 268436184, 536871695, 1073742664, 2147484547, 4294968256, 8589935615 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS For n > 1, also the number of irredundant sets in the complete bipartite graph K_{n,n}. For n > 1, also the number of irredundant sets in the 2 X n rook graph. - Andrew Howroyd, Aug 11 2017 LINKS Eric Weisstein's World of Mathematics, Complete Bipartite Graph Eric Weisstein's World of Mathematics, Irredundant Set Index entries for linear recurrences with constant coefficients, signature (5,-9,7,-2). FORMULA a(n) = 2^(n+1) + n^2 - 1. a(n) = 5*a(n-1) - 9*a(n-2) + 7*a(n-3) - 2*a(n-4). G.f.: (x (1 - x - 2 x^3))/((-1 + x)^3 (-1 + 2 x)). MATHEMATICA Table[2^(n + 1) + n^2 - 1, {n, 0, 40}] LinearRecurrence[{5, -9, 7, -2}, {4, 11, 24, 47}, {0, 20}] CoefficientList[Series[(1 - x - 2 x^3)/((-1 + x)^3 (-1 + 2 x)), {x, 0, 20}], x] PROG (PARI) a(n)=2^(n+1)+n^2-1 \\ Charles R Greathouse IV, Aug 09 2017 CROSSREFS Cf. A290709, A290818. Sequence in context: A160860 A192748 A143075 * A260057 A260150 A258472 Adjacent sequences:  A290704 A290705 A290706 * A290708 A290709 A290710 KEYWORD nonn,easy AUTHOR Eric W. Weisstein, Aug 09 2017 STATUS approved

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Last modified January 23 04:40 EST 2019. Contains 319370 sequences. (Running on oeis4.)