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 A306767 #8 May 23 2019 08:28:29 %S A306767 2,7,5,0,4,7,13,5,0,9,23,17,14,41,11,7,16,55,39,31,8,23,91,19,0,25, %T A306767 109,15,59,49,61,79,10,169,29,17,36,191,131,11,83,71,85,1121,19,47, %U A306767 281,41,0,49,35,79,160,3079,21,13,37,175,3541,209,62,433,55,31,14,23,401,239 %N A306767 Least x > 0 such that (x^2-1)/(y^2-1) = n, where y=A130280(n), or 0 if no such x exists. %F A306767 a(n) = sqrt(n*(A130280(n)^2-1) + 1). %F A306767 a(A130283(n)) = 0. %o A306767 (PARI) a(n, L=10^15) = if(issquare(n), L=2+n^2); for(k=2, L, if((k^2-1)%n==0,if(issquare(1+(k^2-1)/n), return(k)))); %Y A306767 Cf. A130280, A130283. %K A306767 nonn %O A306767 1,1 %A A306767 _Jinyuan Wang_, Apr 13 2019