login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A106497 Numbers whose square is the concatenation of two identical numbers, i.e., of the form NN. 47
36363636364, 45454545455, 54545454546, 63636363637, 72727272728, 81818181819, 90909090910, 428571428571428571429, 571428571428571428572, 714285714285714285715, 857142857142857142858 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

For the corresponding numbers N see A102567.

Numbers of the form j*(10^d + 1)/k where 10^d + 1 == 0 (mod k^2) and k/sqrt(10) < j < k. - David W. Wilson, Nov 09 2006

REFERENCES

R. Ondrejka, Problem 1130: Biperiod Squares, Journal of Recreational Mathematics, Vol. 14:4 (1981-82), 299. Solution by F. H. Kierstead, Jr., JRM, Vol. 15:4 (1982-83), 311-312.

LINKS

David W. Wilson, Table of n, a(n) for n = 1..1098

EXAMPLE

63636363637 is in the sequence because 63636363637^2 = 4049586776940495867769 is 40495867769 written twice.

CROSSREFS

Cf. A092118, A102567.

Sequence in context: A022262 A233849 A116279 * A204097 A295355 A178221

Adjacent sequences:  A106494 A106495 A106496 * A106498 A106499 A106500

KEYWORD

base,nonn

AUTHOR

Lekraj Beedassy, May 04 2005

EXTENSIONS

a(7) from Klaus Brockhaus, May 06 2005

More terms from David W. Wilson, Nov 05 2006

Reference and cross-references added by William Rex Marshall, Nov 12 2010

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 14 01:36 EDT 2019. Contains 327994 sequences. (Running on oeis4.)