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Number of nonnegative integers with property that their base 7/4 expansion (see A024641) has n digits.
0

%I #8 Jul 22 2014 12:36:03

%S 7,7,14,21,42,70,126,217,378,665,1162,2037,3563,6237,10913,19096,

%T 33418,58485,102347,179109,313439,548520,959910,1679839,2939720,

%U 5144510,9002889,15755061,27571355,48249873,84437276,147765233,258589156,452531023,791929292

%N Number of nonnegative integers with property that their base 7/4 expansion (see A024641) has n digits.

%e The numbers 7-13 are represented by 40, 41, 42, 43, 44, 45, 46 respectively in base 7/4. These are the only integers with two digits, and so a(2)=7.

%o (Sage)

%o A=[1]

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

%o A.append(ceil((7-4)/4*sum(A)))

%o [7*x for x in A]

%Y Cf. A024641, A081848.

%K nonn,base

%O 1,1

%A _James Van Alstine_, Jul 21 2014