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 A083043 Integers y such that 11x^2-9y^2=2 for some integer x. 5
 1, 21, 419, 8359, 166761, 3326861, 66370459, 1324082319, 26415275921, 526981436101, 10513213446099, 209737287485879, 4184232536271481, 83474913437943741, 1665314036222603339, 33222805811014123039 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Tanya Khovanova, Recursive Sequences Index entries for linear recurrences with constant coefficients, signature (20,-1) FORMULA G.f.: (1+x)/(1-20*x+x^2). a(n)=20*a(n-1)-a(n-2). a(-1-n)=-a(n). 11*A075839(n)^2-9*a(n)^2=2. a(n+1)=10*a(n)+sqrt(99*a(n)^2+22). - Richard Choulet, Sep 27 2007 MATHEMATICA LinearRecurrence[{20, -1}, {1, 21}, 30] (* Harvey P. Dale, Jun 02 2014 *) PROG (PARI) a(n)=subst(poltchebi(n+1)-poltchebi(n), x, 10)/9 CROSSREFS Sequence in context: A219308 A020534 A106656 * A162807 A097833 A163145 Adjacent sequences:  A083040 A083041 A083042 * A083044 A083045 A083046 KEYWORD easy,nonn AUTHOR Michael Somos, Apr 17 2003 EXTENSIONS Corrected by T. D. Noe, Nov 07 2006 STATUS approved

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