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 A030156 #6 Aug 17 2018 10:48:02
%S A030156 1,9,25,49,81,121,169,361,529,729,961,4761,6561,12321,12769,14161,
%T A030156 16129,18769,32761,34969,56169,72361,74529,76729,78961,96721,212521,
%U A030156 214369,290521,436921,452929,458329,474721,670761,690561,1038361
%N A030156 Odd squares in which parity of digits alternates.
%H A030156 Giovanni Resta, <a href="/A030156/b030156.txt">Table of n, a(n) for n = 1..10000</a>
%t A030156 altQ[n_] := n < 10 || Union[Total /@ Partition[ Mod[ IntegerDigits@n, 2], 2, 1]] == {1}; Select[ Range[1, 2000, 2]^2, altQ[#] &] (* _Giovanni Resta_, Aug 16 2018 *)
%Y A030156 Cf. A030151, A030152, A030155, A030157, A030158.
%K A030156 nonn,base
%O A030156 1,2
%A A030156 _Patrick De Geest_
%E A030156 Offset changed by _Giovanni Resta_, Aug 16 2018