A214488 List of words over {1,3} with equal numbers of 1's and 3's.

13, 31, 1133, 1313, 1331, 3113, 3131, 3311, 111333, 113133, 113313, 113331, 131133, 131313, 131331, 133113, 133131, 133311, 311133, 311313, 311331, 313113, 313131, 313311, 331113, 331131, 331311, 333111

Offset

1,1

Comments

This is to 3 as A214218 is to 2. The subsequence of primes (when interpreted as decimal integers) is A087511.

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Maple

sort([seq(seq((10^(2*d)-1)/9+2*add(10^i, i=s), s=combinat:-choose([$0..(2*d-1)], d)), d=1..4)]); # Robert Israel, Jul 09 2018

Mathematica

Flatten[Table[Sort[FromDigits/@Permutations[PadRight[{}, 2n, {1, 3}]]], {n, 3}]] (* Harvey P. Dale, Aug 03 2014 *)

Crossrefs

Cf. A214218.

Sequence in context: A346022 A227172 A180757 * A247836 A159670 A238736

Adjacent sequences: A214485 A214486 A214487 * A214489 A214490 A214491

Keyword

nonn,base,easy

Author

Jonathan Vos Post, Jul 18 2012

Status

approved