

A043569


Numbers n such that base 2 representation has exactly 2 runs.


6



2, 4, 6, 8, 12, 14, 16, 24, 28, 30, 32, 48, 56, 60, 62, 64, 96, 112, 120, 124, 126, 128, 192, 224, 240, 248, 252, 254, 256, 384, 448, 480, 496, 504, 508, 510, 512, 768, 896, 960, 992, 1008, 1016, 1020, 1022, 1024, 1536, 1792, 1920, 1984, 2016, 2032, 2040, 2044
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OFFSET

1,1


COMMENTS

Numbers n such that binary representation contains the bit string "10" but not "01". Subsequence of A062289; set difference A062289 minus A101082.  Rick L. Shepherd, Nov 29 2004
Mersenne numbers (A000225) times powers of 2 (A000079). Therefore this sequence contains the even perfect numbers (A000396).  Alonso del Arte, Apr 21 2006


LINKS

Lei Zhou, Table of n, a(n) for n = 1..10000


FORMULA

This sequence is twice A023758.  Franklin T. AdamsWatters, Apr 21 2006


MAPLE

a:=proc(n) local nn, nd: nn:=convert(n, base, 2): nd:={seq(nn[j]nn[j1], j=2..nops(nn))}: if n=2 then 2 elif nd={0, 1} then n else fi end: seq(a(n), n=1..2100); # Emeric Deutsch, Apr 21 2006
a:=proc(n) local n2, d: n2:=convert(n, base, 2): d:={seq(n2[j]n2[j1], j=2..nops(n2))}: if n=2 then 2 elif d={0, 1} then n else fi end: seq(a(n), n=1..2100); # Emeric Deutsch, Apr 22 2006


MATHEMATICA

Take[Sort[Flatten[Table[(2^x  1)*(2^y), {x, 32}, {y, 32}]]], 54] (* Alonso del Arte, Apr 21 2006 *)


CROSSREFS

Cf. A062289, A101082.
Sequence in context: A043748 A043756 A043765 * A273131 A249721 A010063
Adjacent sequences: A043566 A043567 A043568 * A043570 A043571 A043572


KEYWORD

nonn,base


AUTHOR

Clark Kimberling


EXTENSIONS

More terms from Rick L. Shepherd, Nov 29 2004


STATUS

approved



