%I #10 Jul 22 2014 12:35:39

%S 9,9,9,9,18,18,27,36,45,54,72,90,117,153,198,252,324,414,531,684,882,

%T 1134,1458,1872,2412,3096,3978,5121,6579,8460,10881,13986,17982,23121,

%U 29727,38223,49140,63180,81234,104445,134280,172647,221976,285399,366939,471780

%N Number of nonnegative integers with property that their base 9/7 expansion (see A024655) has n digits.

%e a(2) = 9 because 70, 71, 72, 73, 74, 75, 76, 77 and 78 are the base 9/7 expansions for the integers 9, 10, 11, 12, 13, 14, 15, 16 and 17 respectively and these are the only integers with 2 digits.

%o (Sage)

%o A=[1]

%o for i in [1..60]:

%o A.append(ceil(((9-7)/7)*sum(A)))

%o [9*x for x in A]

%Y Cf. A024655, A081848, A245356.

%K nonn,base

%O 1,1

%A _Hailey R. Olafson_, Jul 21 2014