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

Author

Jonathan Vos Post, Jul 20 2012

Keywords

• nonn
• base
• easy

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.

Crossrefs

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

Programs

Mathematica

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