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a(0) = 8; for n>0, a(n) = 2*a(n-1) - 1.
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%I #48 Apr 02 2024 11:07:18

%S 8,15,29,57,113,225,449,897,1793,3585,7169,14337,28673,57345,114689,

%T 229377,458753,917505,1835009,3670017,7340033,14680065,29360129,

%U 58720257,117440513,234881025,469762049,939524097,1879048193,3758096385,7516192769,15032385537

%N a(0) = 8; for n>0, a(n) = 2*a(n-1) - 1.

%C An Engel expansion of 2/7 to the base 2 as defined in A181565, with the associated series expansion 2/7 = 2/8 + 2^2/(8*15) + 2^3/(8*15*29) + 2^4/(8*15*29*57) + ... . - _Peter Bala_, Oct 29 2013

%C The initial 8 is the only cube in this sequence. - _Antti Karttunen_, Sep 24 2023

%H Vincenzo Librandi, <a href="/A083686/b083686.txt">Table of n, a(n) for n = 0..1000</a>

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

%F a(n) = 7*2^n + 1. - David Brotherton (dbroth01(AT)aol.com), Jul 29 2003

%F a(n) = 3*a(n-1) - 2*a(n-2), n>1. - _Vincenzo Librandi_, Nov 03 2011

%F G.f.: (8-9*x) / ((1-x)*(1-2*x)). - _Colin Barker_, Sep 20 2016

%F E.g.f.: exp(x)*(1 + 7*exp(x)). - _Stefano Spezia_, Oct 08 2022

%F For n >= 0, A005940(a(n)) = A030078(1+n). - _Antti Karttunen_, Sep 24 2023

%t 7*2^Range[0, 50] + 1 (* _Paolo Xausa_, Apr 02 2024 *)

%o (Magma) [7*2^n+1 : n in [0..30]]; // _Vincenzo Librandi_, Nov 03 2011

%o (PARI) Vec((8-9*x)/((1-x)*(1-2*x)) + O(x^40)) \\ _Colin Barker_, Sep 20 2016

%o (PARI) a(n)=7<<n + 1 \\ _Charles R Greathouse IV_, Sep 20 2016

%Y Cf. A020737, A083575, A083683, A083705, A168596, A181565, A195744.

%Y Cf. A005940, A030078.

%K nonn,easy

%O 0,1

%A _N. J. A. Sloane_, Jun 15 2003