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 A236421 #6 Jan 25 2014 16:46:09 %S A236421 1,4,23,122,743,4851,35579,279644,2390953,22510892,222505867, %T A236421 2236298893,23344760669,248205367341,2905133255201,35462464074278, %U A236421 444339941124303,5844308003978966,78628682982091847,1092345114491353169,15331801966256295943 %N A236421 Largest value of x such that x^2 + y^2 = P, where P is the product of the first n primes of the form 4k + 1, and 0 < x < y. %e A236421 a(3) = 23 because the solutions to x^2 + y^2 = 5*13*17 are (x,y) = (23,24), (9,32), (4,33), (12,31) of which the largest value of x is 23. %Y A236421 Cf. A236381, A236382, A236422. %Y A236421 Cf. A002144. %K A236421 nonn %O A236421 1,2 %A A236421 _Colin Barker_, Jan 25 2014