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A115639 First column of divide-and-conquer triangle A115636. 3

%I #6 Sep 08 2022 08:45:24

%S 1,1,4,4,4,4,16,16,16,16,16,16,16,16,64,64,64,64,64,64,64,64,64,64,64,

%T 64,64,64,64,64,256,256,256,256,256,256,256,256,256,256,256,256,256,

%U 256,256,256,256,256,256,256,256,256,256,256,256,256,256,256,256,256,256

%N First column of divide-and-conquer triangle A115636.

%H G. C. Greubel, <a href="/A115639/b115639.txt">Table of n, a(n) for n = 0..1000</a>

%F G.f.: (1/(1-x))*( 1/4 + (3/4)*Sum_{k>=1} 4^(k-1)*x^(2^k-2) ).

%F a(n) = 4^(floor(log_2(n+2)) - 1). - _G. C. Greubel_, Nov 23 2021

%t 4^(Floor[Log[2, Range[0, 80] +2]] -1) (* _G. C. Greubel_, Nov 23 2021 *)

%o (Magma) [4^(Ilog2(n+2) -1) : n in [0..80] ]; // _G. C. Greubel_, Nov 23 2021

%o (Sage) [4^(floor(log(n+2, 2)) -1) for n in (0..80)] # _G. C. Greubel_, Nov 23 2021

%Y Cf. A000523, A115636.

%K easy,nonn

%O 0,3

%A _Paul Barry_, Jan 27 2006

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Last modified March 28 16:58 EDT 2024. Contains 371254 sequences. (Running on oeis4.)