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A151962
Length of preperiodic part of trajectory of n under iteration of the Kaprekar map in A151949.
11
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
OFFSET
0,11
COMMENTS
Starts to differ from A072137 at n=101. - R. J. Mathar, Jan 23 2026
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 proc:
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 proc:
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
KEYWORD
nonn,base
AUTHOR
N. J. A. Sloane, Aug 19 2009
EXTENSIONS
More terms from R. J. Mathar, Aug 20 2009
STATUS
approved