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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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified December 9 22:27 EST 2019. Contains 329880 sequences. (Running on oeis4.)