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A043682 a(n)=(1/2)(n-th number whose base 2 representation has exactly 4 runs). 1
5, 9, 10, 11, 13, 17, 18, 19, 20, 22, 23, 25, 26, 27, 29, 33, 34, 35, 36, 38, 39, 40, 44, 46, 47, 49, 50, 51, 52, 54, 55, 57, 58, 59, 61, 65, 66, 67, 68, 70, 71, 72, 76, 78, 79, 80, 88, 92, 94, 95, 97, 98, 99, 100, 102, 103, 104, 108, 110 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Numbers with exactly two runs of 1's in binary. - Franklin T. Adams-Watters, Dec 09 2013

LINKS

Table of n, a(n) for n=1..59.

MATHEMATICA

Select[Range[250], Length[Split[IntegerDigits[#, 2]]]==4&]/2 (* Harvey P. Dale, Aug 25 2016 *)

PROG

(PARI) runs(n)=my(s); while(n, n>>=valuation(if(n%2, n+1, n), 2); s++); s

is(n)=runs(n>>valuation(n, 2))==3 \\ Charles R Greathouse IV, Dec 09 2013

CROSSREFS

Cf. A023758, A043683, A043684, A043685, A043686.

Sequence in context: A257739 A094695 A268412 * A111102 A139456 A195684

Adjacent sequences:  A043679 A043680 A043681 * A043683 A043684 A043685

KEYWORD

nonn,base

AUTHOR

Clark Kimberling

STATUS

approved

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Last modified April 19 19:07 EDT 2019. Contains 322290 sequences. (Running on oeis4.)