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A109848
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Highest common factor of n and its 9's complement.
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2
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1, 1, 3, 1, 1, 3, 1, 1, 9, 1, 11, 3, 1, 1, 3, 1, 1, 9, 1, 1, 3, 11, 1, 3, 1, 1, 9, 1, 1, 3, 1, 1, 33, 1, 1, 9, 1, 1, 3, 1, 1, 3, 1, 11, 9, 1, 1, 3, 1, 1, 3, 1, 1, 9, 11, 1, 3, 1, 1, 3, 1, 1, 9, 1, 1, 33, 1, 1, 3, 1, 1, 9, 1, 1, 3, 1, 11, 3, 1, 1, 9, 1, 1, 3, 1, 1, 3, 11, 1, 9, 1, 1, 3, 1, 1, 3, 1, 1, 99, 1, 1, 3
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OFFSET
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1,3
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LINKS
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EXAMPLE
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a(55)=11 because the 9's complement of 55 is 99 - 55 = 44 and the greatest common divisor of 44 and 55 is 11.
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MAPLE
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digs := proc(inp::integer) local resul, shiftinp : resul := 1 : shiftinp := iquo(inp, 10) : while shiftinp > 0 do resul := resul+1 : shiftinp := iquo(shiftinp, 10) : od : RETURN(resul) : end: nin := proc(inp::integer) RETURN(10^digs(inp)-1-inp) : end : for n from 1 to 80 do comp := nin(n) ; #print(n, comp, gcd(n, comp)) ; printf("%d, ", gcd(n, comp)) ; od : # R. J. Mathar, Mar 27 2006
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MATHEMATICA
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hcf[n_]:=Module[{idn=IntegerDigits[n], c9}, c9=FromDigits[PadRight[{}, Length[idn], 9]-idn]; GCD[n, c9]]; Array[hcf, 110] (* Harvey P. Dale, Dec 18 2012 *)
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CROSSREFS
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KEYWORD
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base,easy,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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