A143221 a(0)=1. For n >=1, a(n) = 0 if the binary representation of n occurs at least once in the concatenation of (a(0),a(1),...,a(n-1)). a(n) = 1 otherwise.

1, 0, 0, 1, 0, 1, 1, 1, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 1, 1, 0, 1, 1, 0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 1, 0, 1, 1, 1, 0, 0, 0, 0, 1, 0, 1, 0, 1, 1, 0, 1, 1, 1, 1, 0, 1, 0, 1, 1, 1, 0, 0, 1, 0, 1, 1, 0, 1, 1, 0, 0, 1, 0, 1, 0, 0, 1, 0, 1, 0, 0, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1, 0, 1

Offset

0,1

Links

Robert Israel, Table of n, a(n) for n = 0..10000

Example

The binary representation of 21 is 10101. This occurs in the concatenation of terms a(0) through a(20) like so: 10010111(10101)00010010. So a(21) = 0.

Maple

S:= "1":
for n from 1 to 1000 do
  if StringTools:-Search(convert(convert(n, binary), string), S) = 0 then S:= cat(S, "1") else S:= cat(S, "0") fi
od:
map(parse, StringTools:-Explode(S)); # Robert Israel, May 06 2018

Mathematica

f[l_List]:=Append[l, Boole[StringPosition[ToString[FromDigits[l]], ToString[FromDigits[IntegerDigits[Length[l], 2]]]]=={}]]; Nest[f, {1}, 125] (* Ray Chandler, Nov 09 2008 *)

Crossrefs

Cf. A143220, A143222.

Sequence in context: A104105 A295889 A347523 * A325899 A126999 A306862

Adjacent sequences: A143218 A143219 A143220 * A143222 A143223 A143224

Keyword

base,nonn

Author

Leroy Quet, Jul 30 2008

Extensions

Extended by Ray Chandler, Nov 09 2008

Status

approved