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 A027004 a(n) = T(2*n+1,n+1), T given by A026998. 1
 1, 8, 26, 73, 196, 518, 1361, 3568, 9346, 24473, 64076, 167758, 439201, 1149848, 3010346, 7881193, 20633236, 54018518, 141422321, 370248448, 969323026, 2537720633, 6643838876, 17393795998, 45537549121, 119218851368, 312119004986, 817138163593, 2139295485796 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Colin Barker, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (4,-4,1). FORMULA a(n) = Fibonacci(2*n+3) + 2*Fibonacci(2*n+2) - 3. From Colin Barker, Feb 18 2016: (Start) a(n) = 2^(-n)*(-3*2^n-(3-sqrt(5))^n*(-2+sqrt(5))+(2+sqrt(5))*(3+sqrt(5))^n). a(n) = 4*a(n-1)-4*a(n-2)+a(n-3) for n>2. G.f.: (1+4*x-2*x^2) / ((1-x)*(1-3*x+x^2)). (End) PROG (Magma) [Fibonacci(2*n+3) + 2*Fibonacci(2*n+2) - 3: n in [0..30]]; // Vincenzo Librandi, Apr 18 2011 (PARI) Vec((1+4*x-2*x^2)/((1-x)*(1-3*x+x^2)) + O(x^40)) \\ Colin Barker, Feb 18 2016 CROSSREFS A002878(n+1) - 3. Sequence in context: A296112 A051669 A207101 * A194021 A245126 A278769 Adjacent sequences: A027001 A027002 A027003 * A027005 A027006 A027007 KEYWORD nonn,easy AUTHOR STATUS approved

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Last modified February 7 19:43 EST 2023. Contains 360128 sequences. (Running on oeis4.)