%I
%S 13,19,25,31,37,43,55,61,67,73,79,85,91,103,109,115,121,127,133,151,
%T 157,163,169,175,199,205,211,217,247,253,259,295,301,349,355,361,367,
%U 373,379,385,397,403,409,415,421,427,445,451,457,463,469,493,499,505
%N Numbers whose base7 sum of digits is 7.
%C All of the entries are odd.
%C Subsequence of A016921.  _Michel Marcus_, Sep 03 2013
%C In general, the set of numbers with sum of baseb digits equal to b is a subset of { (b1)*k + 1; k = 2, 3, 4, ... }.  _M. F. Hasler_, Dec 23 2016
%e The 7ary expansion of 13 is (1,6), which has sum of digits 7.
%e The 7ary expansion of 103 is (2,0,5), which has sum of digits 7.
%e 10 is not on the list since the 7ary expansion of 10 is (1,3), which has sum of digits 4 not 7.
%t Select[Range[600],Total[IntegerDigits[#,7]]==7&] (* _Harvey P. Dale_, Aug 18 2014 *)
%o (Sage) [i for i in [0..1000] if sum(Integer(i).digits(base=7))==7]
%o (PARI) select( is(n)=sumdigits(n,7)==7, [1..999]) \\ _M. F. Hasler_, Dec 23 2016
%Y Cf. A018900, A187813.
%Y Cf. A226636 (b = 3), A226969 (b = 4), A227062 (b = 5), A227080 (b = 6), A227092 (b = 7), A227095 (b = 8), A227238 (b = 9), A052224 (b = 10).
%K nonn,base
%O 1,1
%A _Tom Edgar_, Sep 01 2013
