%I #7 Mar 16 2020 16:35:04
%S 0,1,2,3,4,5,6,7,8,7,8,9,10,11,12,13,14,15,12,13,14,15,16,17,18,19,20,
%T 15,16,17,18,19,20,21,22,23,16,17,18,19,20,21,22,23,24,23,24,25,26,27,
%U 28,29,30,31,22,23,24,25,26,27,28,29,30,27,28,29,30,31
%N Sum of digits of n written in fractional base 9/7.
%C The base 9/7 expansion is unique and thus the sum of digits function is well-defined.
%F a(n) = A007953(A024655(n)).
%e In base 9/7 the number 14 is represented by 75 and so a(14) = 7 + 5 = 12.
%o (Sage) # uses [basepqsum from A245355]
%o [basepqsum(9,7,w) for w in [0..200]]
%Y Cf. A007953, A000120, A244040, A024655, A053830.
%K nonn,base
%O 0,3
%A _Hailey R. Olafson_, Jul 18 2014