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Numbers whose squares have an even number of digits.
4

%I #6 Jan 02 2023 12:30:53

%S 4,5,6,7,8,9,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,

%T 51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,

%U 74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92

%N Numbers whose squares have an even number of digits.

%C The sequence of squares starts: 16, 25, 36, 49, 64, 81, 1024, 1089, 1156, 1225, 1296, ...

%H Lars Blomberg, <a href="/A288658/b288658.txt">Table of n, a(n) for n = 1..10000</a>

%H Jeremy Gardiner, <a href="http://list.seqfan.eu/oldermail/seqfan/2016-December/017135.html">Middle digit in square numbers</a>, Seqfan Mailing list, Dec 12 2016.

%Y Cf. A288657, A288659, A288660.

%K nonn,base,easy

%O 1,1

%A _Lars Blomberg_, Jun 13 2017