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a(n) = 4*2^n - 9.
1

%I #21 May 27 2021 18:15:23

%S -1,7,23,55,119,247,503,1015,2039,4087,8183,16375,32759,65527,131063,

%T 262135,524279,1048567,2097143,4194295,8388599,16777207,33554423,

%U 67108855,134217719,268435447,536870903,1073741815,2147483639

%N a(n) = 4*2^n - 9.

%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (3,-2).

%F a(n) = 2*a(n-1) + 9, a(1)= -1. - _Vincenzo Librandi_, Mar 20 2011

%F For n >= 3, a(n) = 8<+>(n+2), where operation <+> is defined in A206853. - _Vladimir Shevelev_, Feb 17 2012

%t Table[4 2^n - 9, {n, 1, 100}]

%t LinearRecurrence[{3,-2},{-1,7},30] (* _Harvey P. Dale_, May 27 2021 *)

%K sign,easy

%O 1,2

%A _Artur Jasinski_, Jan 29 2010