

A072041


a(n) is the smallest number of the form k + reverse(k) for exactly n integers k, or 1 if no such number exists.


11



1, 0, 22, 33, 44, 55, 66, 77, 88, 99, 1111, 1, 2552, 1, 2662, 3443, 2772, 1, 2882, 1, 2992, 3663, 1, 1, 3773, 5445, 1, 3883, 4664, 1, 3993, 1, 4774, 1, 1, 5665, 4884, 1, 1, 1, 4994, 1, 6666, 1, 1, 5885, 1, 1, 6776, 7667, 5995, 1, 1, 1, 6886
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OFFSET

0,3


COMMENTS

The negative terms are conjectural. Moreover they have a rather low degree of confirmation, since due to the timeconsuming computations only numbers from 0 to 65000 have been taken into account. Random tests of larger numbers however seem to indicate, that only selected values of n occur.  In the cognate sequence A071266 two numbers a and b are counted only once, if n = a + b, a = reverse(b), b = reverse(a). Then 33 = 12 + 21 = 30 + 03 has a count of 2 and 44 = 13 + 31 = 22 + 22 = 40 + 04 has a count of 3, so 44 appears in A071266 instead of 33.


LINKS

Table of n, a(n) for n=0..54.
Index entries for sequences related to Reverse and Add!


EXAMPLE

a(0) = 1, since 1 can in no way be written as k + reverse(k); a(1) = 0, since 0 = k + reverse(k) for k = 0; a(3) = 33, since 33 = k + reverse(k) for k = 12, 21 and 30.


CROSSREFS

Cf. A067030, A071266, A072040.
Sequence in context: A157529 A165932 A190588 * A067035 A074054 A067287
Adjacent sequences: A072038 A072039 A072040 * A072042 A072043 A072044


KEYWORD

base,sign


AUTHOR

Klaus Brockhaus, Jun 08 2002


STATUS

approved



