A167036 Squares that remain squares prefixed with a 2.

25, 2500, 7225, 75625, 250000, 722500, 2325625, 7562500, 25000000, 72250000, 232562500, 268140625, 756250000, 2500000000, 7225000000, 23256250000, 26814062500, 68971890625, 75625000000, 250000000000, 722500000000

Offset

1,1

Links

Chai Wah Wu, Table of n, a(n) for n = 1..1000

Example

25 = 5^2 is a square and turns into the square 225 = 15^2 if a 2 is added in front.

Mathematica

Select[Range[850000]^2, IntegerQ[Sqrt[FromDigits[Join[{2}, IntegerDigits[ #]]]]]&] (* Harvey P. Dale, Jan 22 2013 *)

Crossrefs

Sequence in context: A304323 A135057 A324417 * A342107 A145246 A082488

Adjacent sequences: A167033 A167034 A167035 * A167037 A167038 A167039

Keyword

nonn,base

Author

Claudio Meller, Oct 27 2009

Extensions

Keyword:base added by R. J. Mathar, Oct 28 2009

Status

approved