login
Expansion of (1 - x - x^5)/((1 - x - x^5)^2 - 4*x^6).
1

%I #14 Aug 11 2024 15:49:28

%S 1,1,1,1,1,2,7,16,29,46,68,107,191,364,686,1234,2125,3596,6148,10754,

%T 19132,34121,60361,105725,184207,321227,562628,989397,1742190,3064093,

%U 5377732,9424960,16515877,28964243,50840968,89280116,156762020,275136201,482728432

%N Expansion of (1 - x - x^5)/((1 - x - x^5)^2 - 4*x^6).

%H Seiichi Manyama, <a href="/A375284/b375284.txt">Table of n, a(n) for n = 0..1000</a>

%H <a href="/index/Rec#order_10">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1,0,0,2,2,0,0,0,-1).

%F a(n) = 2*a(n-1) - a(n-2) + 2*a(n-5) + 2*a(n-6) - a(n-10).

%F a(n) = Sum_{k=0..floor(n/5)} binomial(2*n-8*k,2*k).

%o (PARI) my(N=40, x='x+O('x^N)); Vec((1-x-x^5)/((1-x-x^5)^2-4*x^6))

%o (PARI) a(n) = sum(k=0, n\5, binomial(2*n-8*k, 2*k));

%Y Cf. A108479, A375279, A375282.

%K nonn

%O 0,6

%A _Seiichi Manyama_, Aug 09 2024