This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A167720 #10 Aug 18 2023 10:50:11
%S A167720 9,441,1521,12321,19881,29241,59049,74529,95481,123201,168921,199809,
%T A167720 227529,263169,288369,328329,356409,370881,385641,471969,480249,
%U A167720 488601,531441,558009,594441,603729,613089,622521,690561,741321,804609,826281
%N A167720 Squares that become a prime number when prefixed with a 5.
%C A167720 Subsequence of squares of A032668. - _Michel Marcus_, Jun 21 2016
%H A167720 G. C. Greubel, <a href="/A167720/b167720.txt">Table of n, a(n) for n = 1..10000</a>
%t A167720 Select[Range[1, 500, 2]^2, PrimeQ[FromDigits[Join[{5}, IntegerDigits[#]]]] &] (* _G. C. Greubel_, Jun 20 2016 *)
%Y A167720 Cf. A032668.
%K A167720 base,nonn
%O A167720 1,1
%A A167720 _Claudio Meller_, Nov 10 2009