|
%I #18 Feb 18 2013 01:00:26
%S 7,70,77,133,266,322,329,392,399,455,511,518,581,588,644,700,707,770,
%T 777,833,966,1015,1085,1141,1148,1204,1274,1330,1337,1463,1526,1596,
%U 1652,1659,1715,1785,1841,1848,1904,1974,2023,2093,2156,2212,2219,2282,2289
%N Multiples of 7 such that the digit sum is divisible by 7.
%C Conjecture: Every century has a representation in the sequence.
%e 1085 = 7*155 and 1 + 0 + 8 + 5 = 14 = 7*2.
%t Select[7*Range[400], Mod[Total[IntegerDigits[#]], 7] == 0 &] (* _T. D. Noe_, Sep 24 2012 *)
%o (JavaScript)
%o function sumarray(arr) {
%o t = 0;
%o for (i = 0; i < arr.length; i++) t += arr[i];
%o return t;
%o }
%o for(s = 7; s < 3000; s += 7) {
%o a = new Array();
%o x = s.toString();
%o for (j = 0; j < x.length; j++) a[j] = Number(x.charAt(j));
%o if (sumarray(a) % 7 == 0) document.write(s + ",");
%o }
%Y Cf. A216995, A216996, A216997, A216998, A217009.
%K nonn,base
%O 1,1
%A _Jon Perry_, Sep 22 2012
|
