A053337 a(n) contains n digits (either '6' or '7') and is divisible by 2^n.
6, 76, 776, 7776, 67776, 667776, 6667776, 66667776, 766667776, 6766667776, 66766667776, 666766667776, 7666766667776, 77666766667776, 777666766667776, 7777666766667776, 77777666766667776, 777777666766667776
Offset: 1
Links
- Ray Chandler, Table of n, a(n) for n = 1..1000
Programs
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Mathematica
Table[Select[FromDigits/@Tuples[{6,7},n],Divisible[#,2^IntegerLength[ #]]&], {n,18}]//Flatten (* Harvey P. Dale, Jul 10 2016 *)
Formula
a(n)=a(n-1)+10^(n-1)*(6+[a(n-1)/2^(n-1) mod 2]) i.e. a(n) ends with a(n-1); if (n-1)-th term is divisible by 2^n then n-th term begins with a 6, if not then n-th term begins with a 7.