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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
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
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;
PROG
(Magma) [n: n in [1..15000 ] | IsSquare(Seqint(Intseq(n) cat Intseq(2)))]; // Marius A. Burtea, Mar 21 2019
KEYWORD
nonn,base
AUTHOR
STATUS
approved