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A214488
List of words over {1,3} with equal numbers of 1's and 3's.
7
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
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
KEYWORD
nonn,base,easy
AUTHOR
Jonathan Vos Post, Jul 18 2012
STATUS
approved