A214532 List of words over {1,9} with equal numbers of 1's and 9's.

19, 91, 1199, 1919, 1991, 9119, 9191, 9911, 111999, 119199, 119919, 119991, 191199, 191919, 191991, 199119, 199191, 199911, 911199, 911919, 911991, 919119, 919191, 919911, 991119, 991191, 991911, 999111, 11119999, 11191999

Offset

1,1

Comments

This is to 9 as A214531 is to 8, as A214530 is to 7, as A214530 is to 6, as A214522 is to 5, as A214521 is to 4, as A214488 is to 3, and as A214218 is to 2.

The subsequence of primes (when interpreted as decimal integers) is A087515.

Links

Table of n, a(n) for n=1..30.

Mathematica

FromDigits/@(Flatten[Permutations/@Table[Join[Table[1, {n}], Table[9, {n}]], {n, 4}], 1]) (* Harvey P. Dale, Aug 20 2014 *)

Crossrefs

Cf. A214218, A214488, A214521, A214522, A214524, A214530, A214531.

Sequence in context: A043232 A044012 A288485 * A118294 A157098 A371532

Adjacent sequences: A214529 A214530 A214531 * A214533 A214534 A214535

Keyword

nonn,base,easy

Author

Jonathan Vos Post, Jul 20 2012

Status

approved