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A281481 a(n) = 2^(n - 1) * (2^n + 1) + 1.

%I A281481 #22 May 02 2025 16:27:51
%S A281481 2,4,11,37,137,529,2081,8257,32897,131329,524801,2098177,8390657,
%T A281481 33558529,134225921,536887297,2147516417,8590000129,34359869441,
%U A281481 137439215617,549756338177,2199024304129,8796095119361,35184376283137,140737496743937,562949970198529
%N A281481 a(n) = 2^(n - 1) * (2^n + 1) + 1.
%H A281481 Colin Barker, <a href="/A281481/b281481.txt">Table of n, a(n) for n = 0..1000</a>
%H A281481 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (7,-14,8).
%F A281481 From _Colin Barker_, Jan 22 2017: (Start)
%F A281481 a(n) = 7*a(n-1) - 14*a(n-2) + 8*a(n-3) for n>2.
%F A281481 G.f.: (2 - 10*x + 11*x^2) / ((1 - x)*(1 - 2*x)*(1 - 4*x)).
%F A281481 (End)
%F A281481 a(n) = A278930(n - 2) for n >= 7. - _Georg Fischer_, Mar 26 2019
%o A281481 (Magma) [2^(n - 1) * (2^n + 1) + 1: n in [0..200]];
%o A281481 (PARI) Vec((2 - 10*x + 11*x^2) / ((1 - x)*(1 - 2*x)*(1 - 4*x)) + O(x^30)) \\ _Colin Barker_, Jan 22 2017
%Y A281481 Similar sequences: A085601 (2^(n + 1) * (2^n + 1) + 1), A092431 (2^(n - 1) * (2^n + 1) - 1), A092440 (2^(n + 1) * (2^n - 1) + 1), A129868 (2^(n - 1) * (2^n - 1) - 1), A134169 (2^(n - 1) * (2^n - 1) + 1), A267816 (2^(n + 1) * (2^n - 1) - 1), A281482 (2^(n + 1) * (2^n + 1) - 1).
%Y A281481 Cf. A278930.
%K A281481 nonn,easy
%O A281481 0,1
%A A281481 _Jaroslav Krizek_, Jan 22 2017