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 A216869 #20 Nov 03 2013 08:27:54 %S A216869 1,25,49 %N A216869 The smallest non-constant arithmetic progression of integer squares of maximal length three. %C A216869 Bremner (2012): "Euler showed that the length of the longest arithmetic progression (AP) of integer squares is equal to three. [See Dickson.] Xarles (2011) investigated APs in number fields, and proved the existence of an upper bound K(d) for the maximal length of an AP of squares in a number field of degree d. He shows that K(2) = 5." See A216870. %D A216869 L. E. Dickson, History of the Theory of Numbers, Vol. II, Chelsea, New York, 1952, pp. 435-440. %H A216869 A. Alvarado and E. H. Goins, <a href="http://arxiv.org/abs/1210.6612">Arithmetic progressions on conic sections</a>, arXiv 2012. %H A216869 A. Bremner, <a href="http://jointmathematicsmeetings.org/amsmtgs/2141_abstracts/1086-11-296.pdf">Arithmetic progressions of squares in cubic fields</a>, Abstract 2012. %F A216869 a(2) - a(1) = a(3) - a(2) = 24. %e A216869 a(1) = 1^2, a(2) = 5^2, a(3) = 7^2. %Y A216869 Cf. A216870, A221671, A221672. %K A216869 nonn,fini,full,bref %O A216869 1,2 %A A216869 _Jonathan Sondow_, Nov 20 2012