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 A050797 #20 Jul 02 2025 16:01:58
%S A050797 3,9,17,19,33,35,73,145,161,163,195,243,393,483,513,721,723,1153,1763,
%T A050797 2177,2305,2593,4803,5185,5833,6273,6963,7057,7395,8713,9523,9603,
%U A050797 10083,12483,13923,14113,15875,17425,17673,19043,20737
%N A050797 Numbers n such that n^2 - 1 is expressible as the sum of two nonzero squares in exactly one way.
%C A050797 If the definition were changed from "nonzero squares" to "nonnegative squares", there would be just one additional term, 1. - _T. D. Noe_, May 27 2008
%H A050797 T. D. Noe, <a href="/A050797/b050797.txt">Table of n, a(n) for n=1..300</a>
%H A050797 Eric Weisstein, <a href="https://mathworld.wolfram.com/SumofSquaresFunction.html">MathWorld: Sum of Squares Function</a>
%H A050797 <a href="/index/Su#ssq">Index entries for sequences related to sums of squares</a>
%e A050797 E.g. 393^2 - 1 = 28^2 + 392^2 only.
%t A050797 twoSquaresQ[ n_] := (r = Reduce [0 < a <= b && n^2 - 1 == a^2 + b^2, {a, b}, Integers]; Head[r] === And); Select[ Range[21000], twoSquaresQ] (* _Jean-François Alcover_, Oct 10 2011 *)
%Y A050797 Cf. A050798, A050795.
%Y A050797 Cf. A000161
%K A050797 nonn,nice
%O A050797 1,1
%A A050797 _Patrick De Geest_, Sep 15 1999
%E A050797 More terms from _James Sellers_