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A076131 a(n) = 2^n*a(n-1)+1, a(0) = 0. 6

%I

%S 0,1,5,41,657,21025,1345601,172236929,44092653825,22575438758401,

%T 23117249288602625,47344126543058176001,193921542320366288900097,

%U 1588605274688440638669594625,26027708820495411423962638336001

%N a(n) = 2^n*a(n-1)+1, a(0) = 0.

%C Base-2 expansion is same as base 10 expansion of A076127.

%H Vincenzo Librandi, <a href="/A076131/b076131.txt">Table of n, a(n) for n = 0..80</a>

%F a(n)=floor(c*2^((n+1)*(n+2)/2)) where c =sum(k>=1, 1/2^A000217(k))=0.6416325... - _Benoit Cloitre_, Nov 01 2002

%t a[0] = 0; a[n_] := 2^n a[n - 1] + 1; Table[ a[n], {n, 0, 13}]

%o (PARI) a(n)=if(n<0,0,subst(Polrev(Vec(sum(k=1,n,x^(k*(k+1)/2)))),x,2))

%o (PARI) a(n)=if(n<1,0,1+a(n-1)*2^n)

%Y Cf. A000217, A073587, A076127, A190405.

%K easy,nonn,base

%O 0,3

%A Kyle Hunter (hunterk(AT)raytheon.com), Oct 31 2002

%E Edited and extended by _Robert G. Wilson v_, Oct 31 2002

%E Formula corrected by _Vaclav Kotesovec_, Aug 11 2012

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Last modified August 3 05:38 EDT 2020. Contains 336197 sequences. (Running on oeis4.)