A273361 Numbers n such that the decimal number concat(6,n) is a square.

4, 25, 76, 241, 400, 561, 724, 889, 1009, 1504, 2001, 2500, 3001, 3504, 4009, 4516, 5025, 5536, 6049, 6564, 7081, 7600, 8121, 8644, 9169, 9696, 11524, 13089, 14656, 16225, 17796, 19369, 20944, 22521, 24100, 25681, 27264, 28849, 30436

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(61), sqrt(70)) * sqrt(10)^k without the leading 6 elements for nonnegative k. - David A. Corneth, May 20 2016

Examples

			76 is a member because 676 = 26^2 is a square.
0 is not a member because 60 is not a square.
		

Links

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

Crossrefs

Cf. A272671, A273357, A273358, A273359, A273360, A273362, A273363, A273364.

Programs

Magma

[n: n in [1..20000 ] | IsSquare(Seqint(Intseq(n) cat Intseq(6)))]; // Marius A. Burtea, Mar 21 2019

Maple

t1:=[];
for k from 1 to 50000 do
if issqr(k+6*10^length(k)) then t1:=[op(t1), k]; fi;
od;
t1;

Mathematica

Select[Range[31000],IntegerQ[Sqrt[FromDigits[Join[{6}, IntegerDigits[ #]]]]]&] (* Harvey P. Dale, Feb 09 2019 *)