

A129120


Undulating Harshad numbers: numbers divisible by the sum of their own digits with decimal expansions in an abab...ab pattern.


0



10, 12, 18, 20, 21, 24, 27, 30, 36, 40, 42, 45, 48, 50, 54, 60, 63, 70, 72, 80, 81, 84, 90, 171, 252, 414, 828, 1010, 1212, 1818, 2020, 2424, 3030, 3636, 4040, 4848, 5050, 5454, 6060, 7070, 7272, 8080, 9090, 10101, 13131, 20202, 23232, 26262, 30303, 39393
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OFFSET

1,1


COMMENTS

This definition of "undulating" is more restrictive than the one used in A033619 and excludes singledigit numbers and numbers of the pattern aaaaaa.  R. J. Mathar, Jun 15 2007


REFERENCES

J. Earls, Red Zen, Lulu Press, NY, 2006, pp. 5657. ISBN: 9781430320173.


LINKS

Table of n, a(n) for n=1..50.


CROSSREFS

Cf. A005349, A003619.
Sequence in context: A247626 A247627 A327709 * A134516 A144363 A051247
Adjacent sequences: A129117 A129118 A129119 * A129121 A129122 A129123


KEYWORD

base,nonn


AUTHOR

Jason Earls, May 25 2007


EXTENSIONS

More terms from R. J. Mathar, Jun 15 2007


STATUS

approved



