A163142 - OEIS

A163142

Integers n such that exactly 80 percent of the digits in base 2 are 1's.

23, 27, 29, 30, 639, 703, 735, 751, 759, 763, 765, 766, 831, 863, 879, 887, 891, 893, 894, 927, 943, 951, 955, 957, 958, 975, 983, 987, 989, 990, 999, 1003, 1005, 1006, 1011, 1013, 1014, 1017, 1018, 1020, 18431, 19455, 19967, 20223, 20351, 20415

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OFFSET

1,1

COMMENTS

The ratio of 1's over 0's is 4:1. Subset of A143909.

LINKS

Zak Seidov, Table of n, a(n) for n = 1..2551

FORMULA

{n: A000120(n)=4*A023416(n) }.

EXAMPLE

The 29 is in the sequence because it reads A007088(29)= 11101 in base 2, and 4 of the 5 digits are 1.

The 1003 is in the sequence because it reads A007088(1003)= 1111101011 in base 2, and 8 of the 10 digits are 1.

MATHEMATICA

f0[n_]:=DigitCount[n, 2, 0]; f1[n_]:=DigitCount[n, 2, 1]; f[n_]:=f1[n]/f0[n]; lst={}; Do[If[f[n]==3, AppendTo[lst, n]], {n, 8!}]; lst

ZS={}; Do[dc=DigitCount[n, 2]; If[dc[[1]]==4*dc[[2]], AppendTo[ZS, n]], {n, 10, 10^6}]; ZS (* Zak Seidov, Jul 28 2009 *)

d80Q[n_]:=Module[{idn2=DigitCount[n, 2]}, idn2[[1]]==4*idn2[[2]]]; Select[ Range[25000], d80Q] (* Harvey P. Dale, Mar 18 2012 *)

CROSSREFS

Cf. A031443, A137254, A163140, A000120, A023416, A143909, A007088.

Sequence in context: A365020 A316724 A160774 * A038772 A188454 A178960

Adjacent sequences: A163139 A163140 A163141 * A163143 A163144 A163145

KEYWORD

nonn,base

AUTHOR

Vladimir Joseph Stephan Orlovsky, Jul 21 2009

EXTENSIONS

Edited by R. J. Mathar, Jul 25 2009

STATUS

approved