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 A076671 #11 Dec 15 2016 08:48:41
%S A076671 5,12,16,30,40,42,56,90,120,126,168,224,360,378,504,550,1320,1386,
%T A076671 1848,1989,2652,2961,3948,5264,8052,9711,12948,17264,24852,31311,
%U A076671 41748,53289,71052,94736,130548,145061,146280,153594,163392,170280,173290
%N A076671 Smallest a(n) > a(n-1) such that a(n)^2+a(n-1)^2 is a perfect square, with a(1)=5.
%C A076671 The sequence is infinite.
%C A076671 If we require the terms to be distinct, but not necessarily increasing, then the sequence "paints itself into a corner" and can't be continued: 5, 12, 9, 40, 30, 16, 63, 60, 11. - _Ivan Neretin_, Dec 15 2016
%H A076671 Ivan Neretin, <a href="/A076671/b076671.txt">Table of n, a(n) for n = 1..1000</a>
%t A076671 Nest[Append[#, k = #[[-1]]; d = Divisors[k^2]; Min@Select[(Reverse@d - d)/2, IntegerQ@# && # > k &]] &, {5}, 40] (* _Ivan Neretin_, Dec 15 2016 *)
%Y A076671 Cf. A076600.
%K A076671 nonn
%O A076671 1,1
%A A076671 _Zak Seidov_, Oct 25 2002