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%I #15 Oct 12 2019 06:51:49
%S 1,4,9,121,484,676,10201,12321,14641,40804,44944,69696,94249,1002001,
%T 1234321,4008004,5221225,6948496,100020001,102030201,104060401,
%U 121242121,123454321,125686521,400080004,404090404,522808225,617323716,942060249,10000200001
%N Palindromic squares with an odd number of digits.
%H Patrick De Geest, <a href="http://www.worldofnumbers.com/subsquar.htm">Subsets of Palindromic Squares</a>
%t id[n_] := IntegerDigits[n]; palQ[n_] := FromDigits[Reverse[id[n]]] == n; t = {}; Do[If[palQ[x = n^2] && OddQ[Length[id[x]]], AppendTo[t, x]],{n, 101000}]; t (* _Jayanta Basu_, May 13 2013 *)
%t Select[Range[100000]^2, PalindromeQ[#] && EvenQ[Floor[Log[10, #]]] &] (* _Alonso del Arte_, Oct 11 2019 *)
%o (Scala) def isPalindromic(n: BigInt): Boolean = n.toString == n.toString.reverse
%o val squares = ((1: BigInt) to (1000000: BigInt)).map(n => n * n)
%o squares.filter(n => isPalindromic(n) && n.toString.length % 2 == 1) // _Alonso del Arte_, Oct 07 2019
%Y Cf. A002779, A028816.
%K nonn,base
%O 1,2
%A _Patrick De Geest_
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