A220948 - OEIS

%I #14 Apr 02 2024 11:39:43

%S 1,4,15,55,200,726,2638,9604,35037,128061,468809,1718446,6305546,

%T 23155863,85089015,312823200,1150506841,4232595095,15574796945,

%U 57320990295,210990647105,776707569176,2859475304889,10527898398268,38763003252400,142727886900676,525547912974105

%N Expansion of (1-x)^2*(1-3*x)/(1-9*x+28*x^2-35*x^3+15*x^4-x^5).

%C A diagonal of the square array A223968.

%H <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (9,-28,35,-15,1).

%F a(n) = A223968(n+2,n).

%F G.f.: (1-x)^2*(1-3*x)/(1-9*x+28*x^2-35*x^3+15*x^4-x^5).

%F a(n) = 9*a(n-1) - 28*a(n-2) + 35*a(n-3) - 15*a(n-4) + a(n-5) with a(0) = 1, a(1) = 4, a(2) = 15, a(3) = 55, a(4) = 200.

%Y Cf. A223968

%K nonn,easy

%O 0,2

%A _Philippe Deléham_, Apr 07 2013