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%I #21 Mar 12 2024 12:16:17
%S 1,6,20,57,154,408,1073,2814,7372,19305,50546,132336,346465,907062,
%T 2374724,6217113,16276618,42612744,111561617,292072110,764654716,
%U 2001892041,5241021410,13721172192,35922495169,94046313318,246216444788
%N a(n) = 4*a(n-1) - 4*a(n-2) + a(n-3), n >= 3; a(0)=1, a(1)=6, a(2)=20.
%C Floretion Algebra Multiplication Program, FAMP Code: 4tessumseq[ + .25'i + .25i' + .25'ii' + .25'jj' + .25'kk' + .25'jk' + .25'kj' + .25e], sumtype: (Y[15], *, vesy)
%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (4,-4,1).
%F a(n) - a(n-1) = A054486(n+1).
%F G.f.: (2*x+1)/((1-x)*(x^2-3*x+1)).
%F a(n) = A027941(n+1) +2*A027941(n). - _R. J. Mathar_, Sep 11 2019
%t Join[{a=1,b=6},Table[c=3*b-1*a+3;a=b;b=c,{n,60}]] (* _Vladimir Joseph Stephan Orlovsky_, Jan 28 2011 *)
%t LinearRecurrence[{4,-4,1},{1,6,20},30] (* _Harvey P. Dale_, Apr 14 2016 *)
%Y Cf. A054486.
%K easy,nonn
%O 0,2
%A _Creighton Dement_, Aug 18 2005
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