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 A097268 #16 Feb 16 2025 08:32:54 %S A097268 5,8,13,17,20,25,29,32,37,40,41,45,52,53,61,65,68,72,73,80,85,89,97, %T A097268 100,101,104,109,113,116,117,125,128,136,137,145,148,149,153,157,160, %U A097268 164,169,173,180,181,185,193,197,200,205,208,212,221,225,229,232,233 %N A097268 Numbers that are both the sum of two nonzero squares and the difference of two nonzero squares. %C A097268 Intersection of A000404 (sum of squares) and A024352 (difference of squares). %C A097268 Also: Numbers of the form x^2+4y^2, where x and y are positive integers. Cf. A154777, A092572, A154778 for analogous sequences. - _M. F. Hasler_, Jan 24 2009 %H A097268 Amiram Eldar, <a href="/A097268/b097268.txt">Table of n, a(n) for n = 1..10000</a> %H A097268 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/SumofSquaresFunction.html">Sum of Squares Function.</a> %o A097268 (PARI) isA097268(n) = forstep( b=2,sqrtint(n-1),2, issquare(n-b^2) && return(1)) \\ _M. F. Hasler_, Jan 24 2009 %Y A097268 Cf. A000404, A024352, A097269, A097270, A097271. %K A097268 nonn %O A097268 1,1 %A A097268 _Ray Chandler_, Aug 19 2004