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a(n)=a(n-1)+a(n-2)+a(n-3)+2a(n-4); a(0)=0,a(1)=1,a(2)=3,a(3)=7.
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%I #15 Jan 02 2024 09:00:02

%S 0,1,3,7,11,23,47,95,187,375,751,1503,3003,6007,12015,24031,48059,

%T 96119,192239,384479,768955,1537911,3075823,6151647,12303291,24606583,

%U 49213167,98426335,196852667,393705335,787410671,1574821343,3149642683

%N a(n)=a(n-1)+a(n-2)+a(n-3)+2a(n-4); a(0)=0,a(1)=1,a(2)=3,a(3)=7.

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

%F O.g.f.: -x(1+2x+3x^2)/((2x-1)(1+x)(x^2+1)). a(n) = (-1)^(n+1)/3 +11*2^n/15 -2*(-1)^[n/2]*A000034(n)/5 . - _R. J. Mathar_, May 24 2008

%t LinearRecurrence[{1,1,1,2},{0,1,3,7},35] (* _Harvey P. Dale_, Apr 20 2011 *)

%Y Cf. A132429.

%K nonn,easy

%O 0,3

%A _Paul Curtz_, May 23 2008

%E More terms from _R. J. Mathar_, May 24 2008