0,3

The base 7/4 expansion is unique, and thus the sum of digits function is well-defined.

Table of n, a(n) for n=0..68.

In base 7/4 the number 7 is represented by 40 and so a(7) = 4 + 0 = 4.

(Sage)

def base74sum(n):

....L=[n]

....i=1

....while L[i-1]>=7:

........x=L[i-1]

........L[i-1]=x.mod(7)

........L.append(4*floor(x/7))

........i+=1

....return sum(L)

[base74sum(y) for y in [0..200]]

Cf. A024641, A053828, A007953.

Sequence in context: A096894 A097751 A070667 * A122416 A134665 A271832

Adjacent sequences: A245346 A245347 A245348 * A245350 A245351 A245352

nonn,base

James Van Alstine, Jul 18 2014

approved