#! perl -slw
use strict;

### Prefer Ones:
### Write n zeros.
### Then, always write a one unless it would cause the repetition of an n-length string;
### In which case, write a zero.

our $N //= 4;

my $t1 = "b${ \(2**$N+$N-1) }";
my $seen = '';
my $mask1 = ( 1<<$N )-1;
my $seq = pack 'Q*', (0) x 100;
my $val = 0;

for( $N .. 2**$N+$N-1 ) {                   ## if N=5; 5 .. 36; if N=6, 6 .. 64+6-1 = 69;
    $val = ( $val << 1 ) & $mask1;
    vec( $seen, $val | 1, 1 ) or do{ $val |= 1; vec( $seq, $_, 1 ) = 1; };
    vec( $seen, $val    , 1 ) = 1;
}
print unpack $t1, $seq;