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A082472 a(1) = 1, a(n) = Sum_{k=1..n-1} a(k)*2^k. 1

%I

%S 1,2,10,90,1530,50490,3281850,423358650,108803173050,55816027774650,

%T 57211428469016250,117226216933014296250,480275810774559571736250,

%U 3934899717675966571235096250,64473331874120712269687052056250

%N a(1) = 1, a(n) = Sum_{k=1..n-1} a(k)*2^k.

%H Vincenzo Librandi, <a href="/A082472/b082472.txt">Table of n, a(n) for n = 1..80</a>

%F a(n+1) = (2^n+1)*a(n) for n>=2.

%F a(n) is asymptotic to c*2^(n*(n-1)/2) where c = Product_{k>=1} (1+1/(2*2^k)) = 1.5894873526.....

%F c = 2*A079555/3. - _Vaclav Kotesovec_, Jun 05 2020

%F G.f. A(x) satisfies: A(x) = x * (1 + A(2*x) / (1 - x)). - _Ilya Gutkovskiy_, Jun 04 2020

%t Join[{1},RecurrenceTable[{a[1]==2,a[n]==(1+2^n) a[-1+n]},a[n], {n,15}]] (* _Harvey P. Dale_, May 11 2011 *)

%o (Sage)

%o from ore_algebra import *

%o R.<x> = QQ['x']; A.<Qx> = OreAlgebra(R, 'Qx', q=2)

%o print((Qx - x - 1).to_list([0,1,2], 10)) # _Ralf Stephan_, Apr 24 2014

%Y Cf. A005329, A079555.

%K nonn

%O 1,2

%A _Benoit Cloitre_, Apr 27 2003

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Last modified September 23 02:49 EDT 2020. Contains 337291 sequences. (Running on oeis4.)