

A046075


Nontrivial undulants; base 10 numbers >100 which are of the form aba, abab, ababa, ..., where a != b.


9



101, 121, 131, 141, 151, 161, 171, 181, 191, 202, 212, 232, 242, 252, 262, 272, 282, 292, 303, 313, 323, 343, 353, 363, 373, 383, 393, 404, 414, 424, 434, 454, 464, 474, 484, 494, 505, 515, 525, 535, 545, 565, 575, 585, 595, 606, 616, 626, 636, 646, 656
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OFFSET

1,1


REFERENCES

C. A. Pickover, ``The Undulation of the Monks.'' Ch. 20 in Keys to Infinity. New York: W.H.Freeman, pp. 159161 1995.
C. A. Pickover, "Wonders of Numbers", Oxford New York 2001, Chapter 52, pp. 123124, 316317.


LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
C. A. Pickover, "Wonders of Numbers, Adventures in Mathematics, Mind and Meaning," Zentralblatt review
Eric Weisstein's World of Mathematics, Undulating Number


PROG

(Haskell)
import Data.Set (fromList, deleteFindMin, insert)
a046075 n = a046075_list !! (n1)
a046075_list = f $ fromList
[100 * a + 10 * b + a  a < [1..9], b < [0..9], b /= a]
where f s = m : f (insert (10 * m + div (mod m 100) 10) s')
where (m, s') = deleteFindMin s
 Reinhard Zumkeller, Apr 29 2015, May 01 2012


CROSSREFS

Cf. A033619, A046076.
Cf. A252664.
Sequence in context: A084430 A182693 * A088882 A135602 A095635 A060916
Adjacent sequences: A046072 A046073 A046074 * A046076 A046077 A046078


KEYWORD

nonn,base


AUTHOR

Eric W. Weisstein


STATUS

approved



