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A227092 Numbers whose base-7 sum of digits is 7. 9

%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 base-7 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 base-b digits equal to b is a subset of { (b-1)*k + 1; k = 2, 3, 4, ... }. - _M. F. Hasler_, Dec 23 2016

%e The 7-ary expansion of 13 is (1,6), which has sum of digits 7.

%e The 7-ary expansion of 103 is (2,0,5), which has sum of digits 7.

%e 10 is not on the list since the 7-ary 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

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Last modified May 29 20:42 EDT 2020. Contains 334710 sequences. (Running on oeis4.)