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A273360
Numbers n such that the decimal number concat(5,n) is a square.
8
29, 76, 184, 329, 476, 625, 776, 929, 1076, 1529, 1984, 2441, 2900, 3361, 3824, 4289, 4756, 5225, 5696, 6169, 6644, 7121, 7600, 8081, 8564, 9049, 9536, 11225, 12656, 14089, 15524, 16961, 18400, 19841, 21284, 22729, 24176, 25625, 27076
OFFSET
1,1
COMMENTS
Elements are squares of integers in (sqrt(51), sqrt(60)) * sqrt(10)^k without the leading 5 elements for nonnegative k. - David A. Corneth, May 20 2016
EXAMPLE
76 is a member because 576 = 24^2 is a square.
0 is not a member because 50 is not a square.
MAPLE
t1:=[];
for k from 1 to 50000 do
if issqr(k+5*10^length(k)) then t1:=[op(t1), k]; fi;
od;
t1;
MATHEMATICA
Select[Range[30000], IntegerQ[Sqrt[5*10^IntegerLength[#]+#]]&] (* Harvey P. Dale, Jan 01 2019 *)
PROG
(Magma) [n: n in [1..10000 ] | IsSquare(Seqint(Intseq(n) cat Intseq(5)))]; // Marius A. Burtea, Mar 21 2019
KEYWORD
nonn,base
AUTHOR
STATUS
approved