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A273357 Numbers n such that the decimal number concat(2,n) is a square. 8
5, 25, 56, 89, 116, 209, 304, 401, 500, 601, 704, 809, 916, 1025, 1316, 1609, 1904, 2201, 2500, 2801, 3104, 3409, 3716, 4025, 4336, 4649, 4964, 5281, 5600, 5921, 6244, 6569, 6896, 7225, 7556, 7889, 8224, 8561, 8900, 9241, 9584, 9929, 10681 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Elements are squares of integers in (sqrt(21), sqrt(30)) * sqrt(10)^k without the leading 2 elements for nonnegative k. - David A. Corneth, May 20 2016

LINKS

Nathan Fox, Table of n, a(n) for n = 1..13085

EXAMPLE

56 is a member because 256 = 16^2 is a square.

0 is not a member because 20 is not a square.

MAPLE

t1:=[];

for k from 1 to 20000 do

if issqr(k+2*10^length(k)) then t1:=[op(t1), k]; fi;

od;

t1;

CROSSREFS

Cf. A272671, A273358, A273359, A273360, A273361, A273362, A273363, A273364.

Sequence in context: A161143 A045576 A146649 * A146412 A228169 A152734

Adjacent sequences:  A273354 A273355 A273356 * A273358 A273359 A273360

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 22 12:46 EDT 2019. Contains 321421 sequences. (Running on oeis4.)