A119909 Numbers n such that n and n^2 written in base 3 are zero-free.
1, 2, 4, 5, 7, 22, 43, 131, 394
Offset: 1
Examples
n: 1, 2, 4, 5, 7, 22, 43, 131, 394 n^2: 1, 4, 16, 25, 49, 484, 1849, 17161, 155236 n written in base 3: 1, 2, 11, 12, 21, 211, 1121, 11212, 112121 n^2 written in base 3: 1,11,121,221,1211,122221,2112111,212112121,21212221111
Crossrefs
Subsequence of A032924.
Programs
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Mathematica
Select[Range[500],DigitCount[#,3,0]==DigitCount[#^2,3,0]==0&] (* Harvey P. Dale, Feb 06 2015 *)
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PARI
isok(n) = vecmin(digits(n, 3)) && vecmin(digits(n^2, 3)); \\ Michel Marcus, Oct 10 2013
Comments