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

1,1

Links

Ray Chandler, Table of n, a(n) for n = 1..1000

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.

Mathematica

Table[Select[FromDigits/@Tuples[{6, 7}, n], Divisible[#, 2^IntegerLength[ #]]&], {n, 18}]//Flatten (* Harvey P. Dale, Jul 10 2016 *)

Crossrefs

Cf. A023409, A050621, A050622, A035014.

Sequence in context: A181343 A241072 A137132 * A199026 A155643 A066797

Adjacent sequences: A053334 A053335 A053336 * A053338 A053339 A053340

Keyword

base,nonn

Author

Henry Bottomley, Mar 06 2000

Status

approved