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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

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

REFERENCES

J. Earls, Red Zen, Lulu Press, NY, 2006, pp. 56-57. ISBN: 978-1-4303-2017-3.

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

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Last modified April 6 18:38 EDT 2020. Contains 333286 sequences. (Running on oeis4.)