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 A162400 #19 Feb 17 2018 12:27:01
%S A162400 1,1,1,4,1,1,1,4,9,1,1,4,1,1,1,16,4,9,9,4,1,1,1,4,25,1,1,4,1,1,1,16,
%T A162400 16,4,4,36,9,9,9,4,9,1,1,4,1,1,1,16,49,25,25,4,1,1,1,4,25,1,1,4,1,1,1,
%U A162400 64,16,16,16,4,4,4,4,36,36,9,9,9,9,9,9,16,81,9,9,4,1,1,1,4,25,1,1,4,1,1,1,16,16,49,49,100,25
%N A162400 a(n) = the largest square that when represented in binary is a substring within the binary representation of n.
%C A162400 a(n) = A162401(n)^2.
%H A162400 Michael De Vlieger, <a href="/A162400/b162400.txt">Table of n, a(n) for n = 1..4096</a>
%F A162400 From _David A. Corneth_, Nov 04 2017: (Start)
%F A162400 a(n^2) = n^2
%F A162400 a(4*n) = 4*a(n)
%F A162400 a(4*n + 2) = a(2*n + 1). (End)
%e A162400 a(8) = 4 since 8 = binary "1000" and the largest square less than or equal to 8, that of 4 = binary "100" appears as the first three bits of "1000". - _Michael De Vlieger_, Nov 04 2017
%t A162400 Table[Block[{k = n, s}, While[SequenceCount[#, IntegerDigits[Set[s, k^2], 2]] == 0, k--]; s] &@ IntegerDigits[n, 2], {n, 101}] (* _Michael De Vlieger_, Nov 04 2017 *)
%Y A162400 Cf. A162401.
%K A162400 base,nonn
%O A162400 1,4
%A A162400 _Leroy Quet_, Jul 02 2009
%E A162400 Corrected and extended by _Sean A. Irvine_, Dec 05 2010