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, 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

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