

A216998


Digit sum of n*7 mod 7.


5



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
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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: A330092 A064812 A282469 * A068118 A076104 A094284
Adjacent sequences: A216995 A216996 A216997 * A216999 A217000 A217001


KEYWORD

nonn,base


AUTHOR

Jon Perry, Sep 22 2012


STATUS

approved



