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 A043687 a(n) = (s(n)-1)/2, where s(n) is the n-th number whose base-2 representation has exactly 3 runs. 3

%I

%S 2,4,5,6,8,9,11,12,13,14,16,17,19,23,24,25,27,28,29,30,32,33,35,39,47,

%T 48,49,51,55,56,57,59,60,61,62,64,65,67,71,79,95,96,97,99,103,111,112,

%U 113,115,119,120,121,123,124,125,126,128,129

%N a(n) = (s(n)-1)/2, where s(n) is the n-th number whose base-2 representation has exactly 3 runs.

%C a(n) = A238246(n) - 1. - _Reinhard Zumkeller_, Feb 20 2014

%H Vincenzo Librandi, <a href="/A043687/b043687.txt">Table of n, a(n) for n = 1..1000</a>

%t (# - 1)/2&/@Select[Range[1000], Length[Split[IntegerDigits[#, 2]]]==3&] (* _Vincenzo Librandi_, Feb 22 2014 *)

%Y Cf. A238246.

%K nonn,base

%O 1,1

%A _Clark Kimberling_

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Last modified March 27 12:09 EDT 2023. Contains 361570 sequences. (Running on oeis4.)