A143220 - OEIS

%I #6 Mar 11 2014 01:32:26

%S 1,1,0,1,0,1,1,0,0,0,1,1,1,1,0,1,0,1,0,0,1,1,1,0,1,0,1,0,0,1,1,0,0,0,

%T 0,1,0,0,1,1,0,1,1,1,1,0,0,1,1,1,0,1,0,1,0,1,0,1,1,0,1,1,0,0,0,0,1,0,

%U 0,0,0,1,0,0,0,0,1,1,1,0,0,0,0,1,1,1,1,0,1,0,0,1,0,0,1,0,0,1,0,1,0,0,0,1,0

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

%e The binary representation of 21 is 10101. This occurs in the concatenation of terms a(0) through a(20) like so: 1101011000111(10101)001. So a(21) = 1.

%t f[l_List]:=Append[l,Boole[StringPosition[ToString[FromDigits[l]],ToString[FromDigits[IntegerDigits[Length[l],2]]]]!={}]];Nest[f,{1},125] [From _Ray Chandler_, Nov 09 2008]

%Y Cf. A118268, A143221, A143222.

%K base,nonn

%O 0,1

%A _Leroy Quet_, Jul 30 2008

%E Extended by _Ray Chandler_, Nov 09 2008