A306767 Least x > 0 such that (x^2-1)/(y^2-1) = n, where y=A130280(n), or 0 if no such x exists.

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, 109, 15, 59, 49, 61, 79, 10, 169, 29, 17, 36, 191, 131, 11, 83, 71, 85, 1121, 19, 47, 281, 41, 0, 49, 35, 79, 160, 3079, 21, 13, 37, 175, 3541, 209, 62, 433, 55, 31, 14, 23, 401, 239

Offset: 1

Author

Jinyuan Wang, Apr 13 2019

Keywords

• nonn

Crossrefs

Cf. A130280, A130283.

Programs

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))));

Formula

a(n) = sqrt(n*(A130280(n)^2-1) + 1).

a(A130283(n)) = 0.