This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A341208 #16 Feb 15 2021 02:03:30 %S A341208 9,12,43,101,276,711,1873,4892,12819,33549,87844,229967,602073, %T A341208 1576236,4126651,10803701,28284468,74049687,193864609,507544124, %U A341208 1328767779,3478759197,9107509828,23843770271,62423801001,163427632716,427859097163,1120149658757 %N A341208 a(n) = F(n+4) * F(n+1) - 4 * (-1)^n where F(n) = A000045(n) are the Fibonacci numbers. %C A341208 First differences of A338225. %C A341208 Also it is second differences between the areas of consecutive rectangles with side lengths F(n+3) and F(n). %D A341208 Burak Muslu, Sayılar ve Bağlantılar, Luna, 2021, p. 51. %H A341208 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (2,2,-1). %F A341208 a(n) = F(n+4) * F(n+1) - 4 * (-1)^n for n > 0. %F A341208 G.f.: x*(9 - 6*x + x^2)/(1 - 2*x - 2*x^2 + x^3). %e A341208 For n = 2, a(2) = F(2+4) * F(2+1) - 4 * (-1)^2 = 8 * 2 - 4 = 12. %o A341208 (PARI) a(n) = fibonacci(n+4)*fibonacci(n+1) - 4*(-1)^n; \\ _Michel Marcus_, Feb 06 2021 %Y A341208 Cf. A000045, A338225 %K A341208 easy,nonn %O A341208 1,1 %A A341208 _Burak Muslu_, Feb 06 2021