%I #7 Mar 16 2020 16:03:14
%S 0,1,2,3,4,5,6,7,5,6,7,8,9,10,11,12,7,8,9,10,11,12,13,14,12,13,14,15,
%T 16,17,18,19,11,12,13,14,15,16,17,18,13,14,15,16,17,18,19,20,18,19,20,
%U 21,22,23,24,25,14,15,16,17,18,19,20,21,13,14,15,16,17
%N Sum of digits of n written in fractional base 8/5.
%C The base 8/5 expansion is unique and thus the sum of digits function is well-defined.
%F a(n) = A007953(A024647(n)).
%e In base 8/5 the number 20 is represented by 524 and so a(20) = 5 + 2 + 4 = 11.
%o (Sage)
%o def basepqsum(p, q, n):
%o L = [n]
%o i = 1
%o while L[i-1]>=p:
%o x=L[i-1]
%o L[i-1]=x.mod(p)
%o L.append(q*(x//p))
%o i+=1
%o return sum(L)
%o [basepqsum(8,5,i) for i in [0..100]]
%Y Cf. A024647, A007953, A000120, A053829, A244040.
%K nonn,base
%O 0,3
%A _Tom Edgar_, Jul 18 2014