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a(n) = a(n-1) - 25*a(n-2), a(0)=1, a(1)=5.
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%I #22 Jan 02 2024 08:56:13

%S 1,5,-20,-145,355,3980,-4895,-104395,17980,2627855,2178355,-63518020,

%T -117976895,1469973605,4419395980,-32329944145,-142814843645,

%U 665433759980,4235804851105,-12400039148395,-118295160426020,191705818283855

%N a(n) = a(n-1) - 25*a(n-2), a(0)=1, a(1)=5.

%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (1,-25).

%F G.f.: (1+4*x)/(1-x+25*x^2).

%F a(n) = Sum_{k=0..n} A133607(n,k)*5^k. - _Philippe Deléham_, Dec 29 2007

%t LinearRecurrence[{1,-25},{1, 5}, 22] (* _Georg Fischer_, May 02 2019 *)

%o (PARI) Vec((1+4*x)/(1-x+25*x^2) + O(x^30)) \\ _Michel Marcus_, May 02 2019

%Y Cf. A133607.

%K easy,sign

%O 0,2

%A _Philippe Deléham_, Dec 28 2007

%E a(10) corrected by _Georg Fischer_, May 02 2019