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A169650 a(1) = 3; thereafter a(n) = 3*a(n-1)+2^n-6.

%I A169650 #9 Jan 22 2018 21:15:46
%S A169650 3,7,23,79,263,847,2663,8239,25223,76687,232103,700399,2109383,
%T A169650 6344527,19066343,57264559,171924743,516036367,1548633383,4646948719,
%U A169650 13942943303,41833024207,125507461223,376539160879,1129651037063,3389020220047,10167194877863
%N A169650 a(1) = 3; thereafter a(n) = 3*a(n-1)+2^n-6.
%H A169650 Todd Silvestri, <a href="/A169650/b169650.txt">Table of n, a(n) for n = 1..2095</a>
%F A169650 a(n) = 4*3^(n-1)-2^(n+1)+3. - _Todd Silvestri_, Dec 15 2014
%p A169650 a:=n->if n=1 then 3 else 3*a(n-1)+2^n-6; fi;
%t A169650 a[n_Integer/;n>=1]:=4*3^(n-1)-2^(n+1)+3 (* _Todd Silvestri_, Dec 15 2014 *)
%t A169650 RecurrenceTable[{a[1]==3,a[n]==3a[n-1]+2^n-6},a,{n,30}] (* _Harvey P. Dale_, Jan 22 2018 *)
%Y A169650 Apart from offset, equals A145563 + 3. Arises in analyzing A169648.
%K A169650 nonn
%O A169650 1,1
%A A169650 _N. J. A. Sloane_, Apr 07 2010