A273360 Numbers n such that the decimal number concat(5,n) is a square.

29, 76, 184, 329, 476, 625, 776, 929, 1076, 1529, 1984, 2441, 2900, 3361, 3824, 4289, 4756, 5225, 5696, 6169, 6644, 7121, 7600, 8081, 8564, 9049, 9536, 11225, 12656, 14089, 15524, 16961, 18400, 19841, 21284, 22729, 24176, 25625, 27076

Offset: 1

Author

Nathan Fox, Brooke Logan, and N. J. A. Sloane, May 20 2016

Keywords

• nonn
• base

Comments

Elements are squares of integers in (sqrt(51), sqrt(60)) * sqrt(10)^k without the leading 5 elements for nonnegative k. - David A. Corneth, May 20 2016

Examples

			76 is a member because 576 = 24^2 is a square.
0 is not a member because 50 is not a square.
		

Links

• Nathan Fox, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A272671, A273357, A273358, A273359, A273361, A273362, A273363, A273364.

Programs

Magma

[n: n in [1..10000 ] | IsSquare(Seqint(Intseq(n) cat Intseq(5)))]; // Marius A. Burtea, Mar 21 2019

Maple

t1:=[];
for k from 1 to 50000 do
if issqr(k+5*10^length(k)) then t1:=[op(t1), k]; fi;
od;
t1;

Mathematica

Select[Range[30000],IntegerQ[Sqrt[5*10^IntegerLength[#]+#]]&] (* Harvey P. Dale, Jan 01 2019 *)