login
Number of nonnegative integers with property that their base 5/2 expansion (see A024632) has n digits.
0

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

%S 5,10,25,60,150,375,940,2350,5875,14685,36715,91785,229465,573660,

%T 1434150,3585375,8963440,22408600,56021500,140053750,350134375,

%U 875335935,2188339840,5470849600,13677124000,34192810000,85482025000,213705062500,534262656250

%N Number of nonnegative integers with property that their base 5/2 expansion (see A024632) has n digits.

%e a(2) = 10 because 20, 21, 22, 23, 24, 40, 41, 42, 43 and 44 are the base 5/2 expansions for the integers 5, 6, 7, 8, 9, 10, 11, 12, 13 and 14 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(((5-2)/2)*sum(A)))

%o [5*x for x in A]

%Y Cf. A081848, A245356, A024632.

%K nonn,base

%O 1,1

%A _Hailey R. Olafson_, Jul 21 2014