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A255246 Fundamental positive solution y = y1(n) of the first class of the Pell equation x^2 - 2*y^2 = -A038873(n), n>=1 (primes congruent to {1,2,7} mod 8). 5
3, 2, 3, 4, 4, 5, 6, 6, 7, 8, 7, 7, 8, 9, 8, 9, 10, 12, 10, 11, 10, 14, 11, 12, 11, 13, 12, 14, 15, 14, 13, 13, 17, 18, 14, 14, 15, 17, 16, 19, 20, 15, 17, 16, 18, 16, 16, 21, 17, 17, 21, 18, 19, 22, 23, 20, 19, 18, 19, 20, 26, 22, 20, 21, 23, 25, 26, 28, 21 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

For the corresponding term x1(n) see A255235(n).

For the primes 1 (mod 8) see A154935, and for the primes 7 (mod 8) see 2*A255232.

See A254934 and A254938 also for the derivation based on the Nagell reference given there.

LINKS

Table of n, a(n) for n=1..69.

FORMULA

A255235(n)^2 - 2*a(n)^2 = -A038873(n) gives the smallest positive (proper) solution of this (generalized) Pell equation.

EXAMPLE

See A255235.

n = 1: 4^2 - 2*3^2 = -2 = -A038873(1),

n = 3: 1^2 - 2*3^2 = 1 - 18 = -17 = -A038873(3).

CROSSREFS

Cf. A038873, A255235, A255247, A255248, A254935, 2*A255232, A002335.

Sequence in context: A077070 A075988 A029150 * A055923 A035634 A091563

Adjacent sequences:  A255243 A255244 A255245 * A255247 A255248 A255249

KEYWORD

nonn,easy

AUTHOR

Wolfdieter Lang, Feb 25 2015

EXTENSIONS

More terms from Colin Barker, Feb 26 2015

STATUS

approved

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Last modified November 17 16:08 EST 2019. Contains 329241 sequences. (Running on oeis4.)