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A157363 686n - 14. 3
672, 1358, 2044, 2730, 3416, 4102, 4788, 5474, 6160, 6846, 7532, 8218, 8904, 9590, 10276, 10962, 11648, 12334, 13020, 13706, 14392, 15078, 15764, 16450, 17136, 17822, 18508, 19194, 19880, 20566, 21252, 21938, 22624, 23310, 23996, 24682 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The identity (4802*n^2-196*n+1)^2-(49*n^2-2*n)*(686*n-14)^2=1 can be written as A157364(n)^2-A157362(n)*a(n)^2=1.

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..10000

Vincenzo Librandi, X^2-AY^2=1

Index entries for linear recurrences with constant coefficients, signature (2,-1).

FORMULA

a(n) = 2*a(n-1) -a(n-2).

G.f.: 14*x*(48+x)/(1-x)^2.

E.g.f.: 14*(1 - (1-49*x)*exp(x)). - G. C. Greubel, Feb 02 2018

MATHEMATICA

LinearRecurrence[{2, -1}, {672, 1358}, 50]

PROG

(MAGMA) I:=[672, 1358]; [n le 2 select I[n] else 2*Self(n-1)-Self(n-2): n in [1..40]];

(PARI) a(n) = 686*n-14.

CROSSREFS

Cf. A157362, A157364.

Sequence in context: A053085 A057695 A233315 * A234732 A057805 A057796

Adjacent sequences:  A157360 A157361 A157362 * A157364 A157365 A157366

KEYWORD

nonn,easy

AUTHOR

Vincenzo Librandi, Feb 28 2009

STATUS

approved

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Last modified March 19 11:10 EDT 2019. Contains 321329 sequences. (Running on oeis4.)