A216998 Digit sum of n*7 mod 7.

0, 5, 3, 3, 1, 6, 6, 4, 2, 0, 0, 5, 3, 3, 6, 4, 4, 2, 0, 5, 5, 3, 1, 1, 6, 4, 4, 2, 5, 3, 3, 1, 6, 6, 4, 2, 2, 0, 5, 3, 3, 1, 4, 4, 2, 0, 0, 5, 3, 1, 1, 6, 4, 4, 2, 0, 0, 3, 1, 6, 6, 4, 2, 2, 0, 5, 5, 3, 1, 6, 6, 2, 0, 0, 5, 3, 3, 1, 6, 4, 4, 2, 0, 0, 5, 1, 1, 6

Offset

1,2

Comments

Zeros correspond to A216994.

Links

Table of n, a(n) for n=1..88.

Example

a(8) corresponds to the digit sum of 56, which is 11, mod 7, so a(8)=4.

Mathematica

Table[Mod[Total[IntegerDigits[7*n]], 7], {n, 100}] (* T. D. Noe, Sep 24 2012 *)

Prog

(JavaScript)
function sumarray(arr) {
t=0;
for (i=0; i<arr.length; i++) t+=arr[i];
return t;
}
k=7;
for(s=1; s<100; s++) {
a=new Array();
x=(s*k).toString();
for (j=0; j<x.length; j++) a[j]=Number(x.charAt(j));
document.write(sumarray(a)%k+", ");
}

Crossrefs

Cf. A216994, A216995, A216996, A216997, A217009.

Sequence in context: A064812 A378206 A282469 * A346469 A068118 A076104

Adjacent sequences: A216995 A216996 A216997 * A216999 A217000 A217001

Keyword

nonn,base

Author

Jon Perry, Sep 22 2012

Status

approved