

A072139


Last term of the preperiodic part of the 'Reverse and Subtract' trajectory of n, or 1 if the trajectory is completely periodic.


2



1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 9, 11, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 22, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 33, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 44, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 55, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 66, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 77, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 88, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 99, 99, 101, 99
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OFFSET

0,3


COMMENTS

'Reverse and Subtract' (cf. A072137) is defined by x > x  reverse(x). For small n the positive terms are the first palindrome in the trajectory of n, so this sequence is a weak analog of A033865, which uses 'Reverse and Add'. a(1012) = 8712 is the first nonpalindrome (cf. A072140). For k in A072140, A072141 or A072142 we have a(k) = 1.


LINKS

Table of n, a(n) for n=0..102.


EXAMPLE

a(0) = 1, since 0 > 0  0 = 0, the preperiodic part is empty; a(12) = 9, since 12 > 12  21 = 9.


CROSSREFS

Cf. A033865, A072137, A072140, A072141, A072142.
Sequence in context: A081600 A239092 A017884 * A266325 A262087 A261914
Adjacent sequences: A072136 A072137 A072138 * A072140 A072141 A072142


KEYWORD

base,easy,sign


AUTHOR

Klaus Brockhaus, Jun 24 2002


STATUS

approved



