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A216998
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Digit sum of n*7 mod 7.
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5
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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
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1,2
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COMMENTS
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LINKS
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EXAMPLE
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a(8) corresponds to the digit sum of 56, which is 11, mod 7, so a(8)=4.
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MATHEMATICA
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Table[Mod[Total[IntegerDigits[7*n]], 7], {n, 100}] (* T. D. Noe, Sep 24 2012 *)
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PROG
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(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+", ");
}
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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