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Expansion of (1-x+x^2)/(1-2x+2x^2-x^3-x^4).
2

%I #18 Jun 16 2024 13:05:08

%S 1,1,1,1,2,4,6,7,8,12,21,33,44,55,76,119,185,263,351,480,706,1066,

%T 1551,2156,2982,4269,6281,9162,13013,18252,25921,37513,54449,78045,

%U 110626,157124,225490,325403,467576,666960,949661,1358381,1951976,2803811

%N Expansion of (1-x+x^2)/(1-2x+2x^2-x^3-x^4).

%H Harvey P. Dale, <a href="/A096750/b096750.txt">Table of n, a(n) for n = 0..1000</a>

%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (2,-2,1,1).

%F a(n) = 2*a(n-1)-2*a(n-2)+a(n-3)+a(n-4).

%t CoefficientList[Series[(1-x+x^2)/(1-2x+2x^2-x^3-x^4),{x,0,50}],x] (* or *) LinearRecurrence[ {2,-2,1,1},{1,1,1,1},50] (* _Harvey P. Dale_, Jun 16 2024 *)

%Y Cf. A003522.

%K nonn,easy

%O 0,5

%A _Paul Barry_, Jul 07 2004