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A273362 Numbers n such that the decimal number concat(7,n) is a square. 8
29, 84, 225, 396, 569, 744, 921, 1289, 1824, 2361, 2900, 3441, 3984, 4529, 5076, 5625, 6176, 6729, 7284, 7841, 8400, 8961, 9524, 10649, 12336, 14025, 15716, 17409, 19104, 20801, 22500, 24201, 25904, 27609, 29316, 31025, 32736, 34449 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Elements are squares of integers in (sqrt(71), sqrt(80)) * sqrt(10)^k without the leading 7 elements for nonnegative k. - David A. Corneth, May 20 2016

LINKS

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

EXAMPLE

84 is a member because 784 = 28^2 is a square.

0 is not a member because 70 is not a square.

MAPLE

t1:=[];

for k from 1 to 50000 do

if issqr(k+7*10^length(k)) then t1:=[op(t1), k]; fi;

od;

t1;

MATHEMATICA

Select[Range[35000], IntegerQ[Sqrt[7*10^IntegerLength[#]+#]]&] (* Harvey P. Dale, Feb 10 2019 *)

CROSSREFS

Cf. A272671, A273357, A273358, A273359, A273360, A273361, A273363, A273364.

Sequence in context: A156784 A142592 A255187 * A195314 A323218 A124784

Adjacent sequences:  A273359 A273360 A273361 * A273363 A273364 A273365

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 10:07 EDT 2019. Contains 321421 sequences. (Running on oeis4.)