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A199338 y-values in the solution to 15*x^2 - 14 = y^2. 2
1, 11, 19, 89, 151, 701, 1189, 5519, 9361, 43451, 73699, 342089, 580231, 2693261, 4568149, 21203999, 35964961, 166938731, 283151539, 1314305849, 2229247351, 10347508061, 17550827269, 81465758639, 138177370801, 641378561051, 1087868139139, 5049562729769 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

When are both n+1 and 15*n+1 perfect squares? This problem gives the equation 15*x^2-14=y^2.

Essentially the same as A103201. - R. J. Mathar, Nov 11 2011

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..200

Index entries for linear recurrences with constant coefficients, signature (0, 8, 0, -1).

FORMULA

a(n+4) = 8*a(n+2) - a(n) with a(1)=1, a(2)=11, a(3)=19, a(4)=89.

G.f.: x*(1+x)*(1+10*x+x^2)/(1-8*x^2+x^4). - Bruno Berselli, Nov 08 2011

MATHEMATICA

LinearRecurrence[{0, 8, 0, -1}, {1, 11, 19, 89}, 50]

PROG

(MAGMA) m:=29; R<x>:=PowerSeriesRing(Integers(), m); Coefficients(R!(x*(1+x)*(1+10*x+x^2)/(1-8*x^2+x^4))); // Bruno Berselli, Nov 08 2011

CROSSREFS

Cf. A199336.

Sequence in context: A229542 A039365 A103201 * A043188 A043968 A199329

Adjacent sequences:  A199335 A199336 A199337 * A199339 A199340 A199341

KEYWORD

nonn,easy

AUTHOR

Sture Sjöstedt, Nov 08 2011

STATUS

approved

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Last modified October 20 05:51 EDT 2020. Contains 337897 sequences. (Running on oeis4.)