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 A341208 a(n) = F(n+4) * F(n+1) - 4 * (-1)^n where F(n) = A000045(n) are the Fibonacci numbers. 3
 9, 12, 43, 101, 276, 711, 1873, 4892, 12819, 33549, 87844, 229967, 602073, 1576236, 4126651, 10803701, 28284468, 74049687, 193864609, 507544124, 1328767779, 3478759197, 9107509828, 23843770271, 62423801001, 163427632716, 427859097163, 1120149658757 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS First differences of A338225. Also it is second differences between the areas of consecutive rectangles with side lengths F(n+3) and F(n). REFERENCES Burak Muslu, Sayılar ve Bağlantılar, Luna, 2021, p. 51. LINKS Table of n, a(n) for n=1..28. Index entries for linear recurrences with constant coefficients, signature (2,2,-1). FORMULA a(n) = F(n+4) * F(n+1) - 4 * (-1)^n for n > 0. G.f.: x*(9 - 6*x + x^2)/(1 - 2*x - 2*x^2 + x^3). EXAMPLE For n = 2, a(2) = F(2+4) * F(2+1) - 4 * (-1)^2 = 8 * 2 - 4 = 12. PROG (PARI) a(n) = fibonacci(n+4)*fibonacci(n+1) - 4*(-1)^n; \\ Michel Marcus, Feb 06 2021 CROSSREFS Cf. A000045, A338225 Sequence in context: A024877 A120991 A253088 * A328120 A072308 A140145 Adjacent sequences: A341205 A341206 A341207 * A341209 A341210 A341211 KEYWORD easy,nonn AUTHOR Burak Muslu, Feb 06 2021 STATUS approved

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Last modified October 4 15:50 EDT 2023. Contains 365885 sequences. (Running on oeis4.)