A216996 Numbers n such that the digit sum of n*7 is a multiple of 7.

1, 10, 11, 19, 38, 46, 47, 56, 57, 65, 73, 74, 83, 84, 92, 100, 101, 110, 111, 119, 138, 145, 155, 163, 164, 172, 182, 190, 191, 209, 218, 228, 236, 237, 245, 255, 263, 264, 272, 282, 289, 299, 308, 316, 317, 326, 327, 335, 343, 344, 353, 354, 362, 380, 381

Offset: 1

Author

Jon Perry, Sep 22 2012

Keywords

• nonn
• base

Comments

If n is in the sequence, so are 10*n and 10*n+1. - Robert Israel, Mar 08 2018

Examples

			7*19 = 133 and 1+3+3=7.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A216994, A216995, A216997, A216998, A217009.

Programs

JavaScript

function sumarray(arr) {
t=0;
for (i=0;i
				

Maple

filter:= n -> convert(convert(7*n,base,10),`+`) mod 7 = 0:
select(filter, [$1..1000]); # Robert Israel, Mar 08 2018

Mathematica

Select[Range[500], Mod[Total[IntegerDigits[7*#]], 7] == 0 &] (* T. D. Noe, Sep 24 2012 *)