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A006886 Kaprekar numbers: n such that n=q+r and n^2=q*10^m+r, for some m >= 1, q>=0 and 0<=r<10^m, with n != 10^a, a>=1.
(Formerly M4625)
+0
12
1, 9, 45, 55, 99, 297, 703, 999, 2223, 2728, 4879, 4950, 5050, 5292, 7272, 7777, 9999, 17344, 22222, 38962, 77778, 82656, 95121, 99999, 142857, 148149, 181819, 187110, 208495, 318682, 329967, 351352, 356643, 390313, 461539, 466830, 499500, 500500, 533170 (list; graph; listen)
OFFSET

1,2

COMMENT

4879 and 5292 are in this sequence but not in A053816.

REFERENCES

D. Kaprekar, On Kaprekar numbers, J. Rec. Math., 13 (1980-1981), 81-82.

D. Wells, The Penguin Dictionary of Curious and Interesting Numbers. Penguin Books, NY, 1986, 151.

Douglas E. Iannucci and Bertrum Foster, Kaprekar Triples, Journal of Integer Sequences, Vol. 8 (2005), Article 05.4.8.

LINKS

T. D. Noe, Table of n, a(n) for n=1..1019

Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.

D. E. Iannucci, Journal of Integer Sequences, Vol. 3, 2000, #1.2, The Kaprekar Numbers

W. Schneider, Kaprekar Numbers

G. Villemin's Almanach of Numbers, Procede de Kaprekar

EXAMPLE

703 is Kaprekar because 703=494+209, 703^2=494209.

CROSSREFS

See A053816 for another version.

Cf. A037042, A053394, A053395, A053396, A053397, A045913, A003052.

Sequence in context: A124983 A087969 A044111 this_sequence A053816 A044492 A067536

Adjacent sequences: A006883 A006884 A006885 this_sequence A006887 A006888 A006889

KEYWORD

nonn,nice,base,easy

AUTHOR

mrob(AT)mrob.com (Robert P Munafo)

EXTENSIONS

More terms from Michel ten Voorde (seqfan(AT)tenvoorde.org) Apr 11 2001

4879 and 5292 added by Larry Reeves (larryr(AT)acm.org), Apr 24, 2001

38962 added by Larry Reeves (larryr(AT)acm.org), May 23 2002

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Last modified July 25 07:41 EDT 2008. Contains 142293 sequences.


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