A245356 - OEIS

%I #8 Oct 02 2021 06:02:46

%S 4,4,4,4,8,8,12,16,20,28,36,48,64,88,116,156,208,276,368,492,656,872,

%T 1164,1552,2068,2760,3680,4904,6540,8720,11628,15504,20672,27560,

%U 36748,48996,65328,87104,116140,154852,206472,275296,367060,489412,652552,870068

%N Number of numbers whose base-4/3 expansion (see A024631) has n digits.

%F a(n) = 4*A072493(n).

%e a(3) = 4 because 320, 321, 322, and 323 are the base-4/3 expansions for the numbers 9, 10, 11, and 12 respectively and these are the only numbers with 3 digits.

%o (Sage)

%o A=[1]

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

%o     A.append(ceil(((4-3)/3)*sum(A)))

%o [4*x for x in A]

%Y Cf. A072493, A024631, A081848.

%K nonn,base

%O 1,1

%A _Hailey R. Olafson_, Jul 18 2014