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%I #19 May 16 2020 02:54:51
%S 5,18,59,184,561,1694,5095,15300,45917,137770,413331,1240016,3720073,
%T 11160246,33480767,100442332,301327029,903981122,2711943403,
%U 8135830248,24407490785,73222472398,219667417239,659002251764,1977006755341
%N a(n) = 2*3^n + 3^(n-1) - (n+1).
%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (5,-7,3).
%F O.g.f.: -x*(5-7*x+4*x^2)/((-1+x)^2*(-1+3*x)). - _R. J. Mathar_, Jan 07 2008
%F a(n) = A108765(n-1) + A108765(n). - _Klaus Purath_, Apr 13 2020
%e a(3) = 2*3^3 + 3^2 - 4 = 2*27 + 9 - 4.
%p A133648:=n->2*3^n+3^(n-1)-(n+1): seq(A133648(n), n=1..40); # _Wesley Ivan Hurt_, Apr 18 2017
%t Table[2*3^n + 3^(n - 1) - (n + 1), {n, 1, 50}] (* _Stefan Steinerberger_, Sep 20 2007 *)
%Y Cf. A000244, A108765, A133649 (inverse binomial transform).
%K nonn,easy
%O 1,1
%A _Gary W. Adamson_, Sep 19 2007
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