A130177 For p = the n-th prime, a(n) = the least prime q greater than p+2 such that (p^2+q^2)/2 - 1 is a square, or a(n) = 0 if there is no such prime.

0, 11, 263, 59, 23, 101, 109, 1278886952463697, 151, 193, 79, 269, 277, 311, 0, 179, 83, 83003, 479, 487, 181, 563, 571, 613, 1201, 157, 141509, 739, 773, 479, 6858037981, 907, 1291, 983, 227, 6133, 1109, 1151, 54331, 1201, 431, 307, 1327

Offset

1,2

Links

Don Reble, Table of n, a(n) for n=1..787

Dean Hickerson, Proof that a(15) = 0

Number Theory Web, Solving x^2-Dy^2=N

J. P. Robertson, Solving the Generalized Pell Equation

Example

a(3) = 263 because (5^2+263^2)/2-1 = 186^2.
a(4) = 59 because (7^2+59^2)/2-1 = 42^2.
a(5) = 23 because (11^2+23^2)/2-1 = 18^2.

Crossrefs

Sequence in context: A142208 A168466 A091159 * A356212 A100841 A003389

Adjacent sequences: A130174 A130175 A130176 * A130178 A130179 A130180

Keyword

nonn

Author

Nick Hobson, May 14 2007

Extensions

Edited by T. D. Noe and Don Reble, May 14 2007

Status

approved