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A227911
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Number of remainders occurring only once when dividing n by 1,2,...n.
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1
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1, 0, 1, 1, 1, 2, 2, 2, 3, 2, 2, 4, 4, 4, 5, 4, 4, 5, 5, 6, 7, 6, 6, 7, 7, 6, 7, 7, 7, 9, 9, 9, 10, 9, 9, 10, 10, 10, 11, 10, 10, 12, 12, 13, 14, 13, 13, 14, 14, 13, 14, 14, 14, 15, 15, 15, 16, 15, 15, 17, 17, 17, 18, 17, 17, 18, 18, 19, 20, 19, 19, 20, 20, 20, 21, 21, 21, 22, 22, 22, 23, 22, 22, 24, 24, 23
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OFFSET
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1,6
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COMMENTS
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LINKS
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EXAMPLE
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9 divided by 1,2...9 gives the remainders 0,1,0,1,4,3,2,1,0 of which 2,3,4 occur only once, so a(9)=3.
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MATHEMATICA
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Table[Count[Tally[Mod[n, Range[n]]], _?(#[[2]]==1&)], {n, 90}] (* Harvey P. Dale, Aug 17 2023 *)
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PROG
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(PARI) a(n)=v=vector(n+1); for(d=1, n, t=(n%d)+1; v[t]=v[t]+1); sum(i=1, n, v[i]==1)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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