A109848 Highest common factor of n and its 9's complement.

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

Offset

1,3

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Example

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.

Maple

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

Mathematica

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 *)

Crossrefs

Cf. A109847, A084021.

Sequence in context: A038500 A091840 A083985 * A371098 A104146 A326405

Adjacent sequences: A109845 A109846 A109847 * A109849 A109850 A109851

Keyword

base,easy,nonn

Author

Amarnath Murthy, Jul 06 2005

Extensions

Corrected and extended by R. J. Mathar, Mar 27 2006

More terms from Joshua Zucker, May 03 2006

Status

approved