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A273361 Numbers n such that the decimal number concat(6,n) is a square. 8
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

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

LINKS

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

EXAMPLE

76 is a member because 676 = 26^2 is a square.

0 is not a member because 60 is not a square.

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 *)

CROSSREFS

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

Sequence in context: A180569 A302821 A125309 * A266126 A303514 A041991

Adjacent sequences:  A273358 A273359 A273360 * A273362 A273363 A273364

KEYWORD

nonn,base

AUTHOR

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

STATUS

approved

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Last modified March 23 04:46 EDT 2019. Contains 321422 sequences. (Running on oeis4.)