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A156605 a(n) = (4^n + 20)/3. 2

%I

%S 7,8,12,28,92,348,1372,5468,21852,87388,349532,1398108,5592412,

%T 22369628,89478492,357913948,1431655772,5726623068,22906492252,

%U 91625968988,366503875932,1466015503708,5864062014812,23456248059228,93824992236892,375299968947548

%N a(n) = (4^n + 20)/3.

%H Vincenzo Librandi, <a href="/A156605/b156605.txt">Table of n, a(n) for n = 0..1000</a>

%F a(n) = -A156591(2n+1).

%F a(n) = 4 + A154879(2n) = 7 + A002450(n).

%F a(n) = 4*a(n-1) - 20, n > 0.

%F G.f.: (7-27*x)/((1-x)*(1-4*x)). - _R. J. Mathar_, Feb 23 2009

%o (MAGMA) [(4^n+20)/3: n in [0..35]]; // _Vincenzo Librandi_, Jul 24 2011

%K nonn,easy

%O 0,1

%A _Paul Curtz_, Feb 11 2009

%E Edited and extended by _R. J. Mathar_, Feb 23 2009

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Last modified June 21 07:27 EDT 2021. Contains 345358 sequences. (Running on oeis4.)