A151962 - OEIS

A151962

Length of preperiodic part of trajectory of n under iteration of the Kaprekar map in A151949.

0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 2, 6, 4, 5, 3, 3, 5, 4, 6, 2, 1, 2, 6, 4, 5, 3, 3, 5, 4, 6, 2, 1, 2, 6, 4, 5, 3, 3, 5, 4, 6, 2, 1, 2, 6, 4, 5, 3, 3, 5, 4, 6, 2, 1, 2, 6, 4, 5, 3, 3, 5, 4, 6, 2, 1, 2, 6, 4, 5, 3, 3, 5, 4, 6, 2, 1, 2, 6, 4, 5, 3, 3, 5, 4, 6, 2, 1, 2, 6, 4, 5, 3, 3, 5, 4, 6, 2

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OFFSET

0,11

LINKS

Joseph Myers, Table of n, a(n) for n = 0..1000

Index entries for the Kaprekar map

EXAMPLE

13 -> 18 -> 63 -> 27 -> 45 -> 9 -> 0 -> 0, so a(13)=6.

MAPLE

A151949 := proc(n)

local tup;

tup := sort(convert(n, base, 10)) ;

add( (op(i, tup)-op(-i, tup)) *10^(i-1), i=1..nops(tup)) :

end:

A151962 := proc(n)

local tra, x ;

tra := [n] ;

x := n ;

while true do

x := A151949(x) ;

if member(x, tra, 'l') then

RETURN(l-1) ;

fi;

tra := [op(tra), x] :

od:

end:

seq(A151962(n), n=0..120) ;

# R. J. Mathar, Aug 20 2009

CROSSREFS

Cf. A151949, A151963. Strictly different from A072137.

In other bases: A164885 (base 2), A164995 (base 3), A165014 (base 4), A165034 (base 5), A165053 (base 6), A165073 (base 7), A165092 (base 8), A165112 (base 9). - Joseph Myers, Sep 05 2009

Sequence in context: A126093 A065279 A343383 * A072137 A061569 A294523

Adjacent sequences: A151959 A151960 A151961 * A151963 A151964 A151965

KEYWORD

nonn,base

AUTHOR

N. J. A. Sloane, Aug 19 2009

EXTENSIONS

More terms from R. J. Mathar, Aug 20 2009

STATUS

approved