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A175262 Those positive integers that when written in binary contain an odd number of digits, the middle digit being a 1. 1
1, 6, 7, 20, 21, 22, 23, 28, 29, 30, 31, 72, 73, 74, 75, 76, 77, 78, 79, 88, 89, 90, 91, 92, 93, 94, 95, 104, 105, 106, 107, 108, 109, 110, 111, 120, 121, 122, 123, 124, 125, 126, 127, 272, 273, 274, 275, 276, 277, 278, 279, 280, 281, 282, 283, 284, 285, 286, 287 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
MAPLE
isA175262 := proc(n) local dgs ; dgs := convert(n, base, 2) ; if type(nops(dgs), 'odd') then return ( op( (nops(dgs)+1)/2 , dgs) = 1 ) ; else false ; end if; end proc: for n from 1 to 400 do if isA175262(n) then printf("%d, ", n) ; end if; end do: # R. J. Mathar, Mar 29 2010
MATHEMATICA
ondQ[n_]:=Module[{id=IntegerDigits[n, 2], len}, len=Length[id]; OddQ[len] && id[[(len+1)/2]]==1]; Select[Range[300], ondQ] (* Harvey P. Dale, Apr 01 2018 *)
CROSSREFS
Cf. A175263.
Sequence in context: A287760 A305675 A210605 * A345911 A081348 A002361
KEYWORD
base,nonn
AUTHOR
Leroy Quet, Mar 16 2010
EXTENSIONS
More terms from R. J. Mathar, Mar 29 2010
STATUS
approved

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Last modified June 18 17:51 EDT 2024. Contains 373483 sequences. (Running on oeis4.)