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A068810 Numbers n such that n and its 10's complement are both squares, i.e., n and 10^k - n (where k is the number of digits in n) are squares. 1
1, 9, 36, 64, 100, 324, 676, 900, 3600, 6400, 9216, 10000, 32400, 67600, 90000, 99856, 123904, 360000, 640000, 876096, 921600, 1000000, 3240000, 3968064, 6031936, 6760000, 9000000, 9985600, 12390400, 28901376, 36000000, 64000000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Terms from V. P. Singh. If k in sequence so is k * 100^m. See A068075 for the smaller of the primitive pairs.

LINKS

Table of n, a(n) for n=1..32.

EXAMPLE

324 = 18^2 is a member as 1000 - 324 = 676 = 26^2.

MATHEMATICA

Select[Range[10^4]^2, IntegerQ[Sqrt[10^(IntegerLength[#]) - #]] &] (* Jayanta Basu, Aug 05 2013 *)

CROSSREFS

Cf. A068075.

Sequence in context: A169580 A258844 A294952 * A077115 A297584 A073946

Adjacent sequences:  A068807 A068808 A068809 * A068811 A068812 A068813

KEYWORD

nonn,base

AUTHOR

Amarnath Murthy, Mar 07 2002

EXTENSIONS

Edited and extended by Robert G. Wilson v, Mar 20 2002

STATUS

approved

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Last modified November 14 04:56 EST 2019. Contains 329110 sequences. (Running on oeis4.)