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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. 1
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 (list; graph; refs; listen; history; text; internal format)
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 * A100841 A003389 A243210

Adjacent sequences:  A130174 A130175 A130176 * A130178 A130179 A130180

KEYWORD

nonn

AUTHOR

Nick Hobson (nickh(AT)qbyte.org), May 14 2007

EXTENSIONS

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

STATUS

approved

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Last modified May 12 19:15 EDT 2021. Contains 343829 sequences. (Running on oeis4.)