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 *)
KEYWORD
base,nonn
AUTHOR
Henry Bottomley, Mar 06 2000
STATUS
approved