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 A371843 #45 Apr 15 2024 12:31:50
%S A371843 1,4,6,9,16,24,41,64,106,169,276,444,721,1164,1886,3049,4936,7984,
%T A371843 12921,20904,33826,54729,88556,143284,231841,375124,606966,982089,
%U A371843 1589056,2571144,4160201,6731344,10891546,17622889,28514436,46137324,74651761,120789084,195440846
%N A371843 a(n) = 5*Fibonacci(n) + (-1)^n.
%H A371843 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (0,2,1).
%F A371843 a(n) = a(n-2) + A022088(n-1).
%F A371843 a(n) = 2*a(n-2) + a(n-3).
%F A371843 a(n) = A022088(n) + A033999(n).
%F A371843 a(n) = - a(n-3) + 10*A000045(n-1) for n >= 3.
%F A371843 G.f.: (1+2*x)^2/((1+x)*(1-x-x^2)). - _Joerg Arndt_, Apr 13 2024
%e A371843 a(3) = 2*4 + 1 = 9. Also a(3) = -1 + 10*1 = 9.
%t A371843 LinearRecurrence[{0, 2, 1}, {1, 4, 6}, 50] (* _Amiram Eldar_, Apr 11 2024 *)
%Y A371843 Cf. A000045, A022088, A033999, A097133.
%K A371843 nonn,easy
%O A371843 0,2
%A A371843 _Paul Curtz_, Apr 08 2024