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 A158249 256n^2 - 2n. 2
 254, 1020, 2298, 4088, 6390, 9204, 12530, 16368, 20718, 25580, 30954, 36840, 43238, 50148, 57570, 65504, 73950, 82908, 92378, 102360, 112854, 123860, 135378, 147408, 159950, 173004, 186570, 200648, 215238, 230340, 245954, 262080, 278718, 295868 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The identity (256*n-1)^2-(256*n^2-2*n)*(16)^2=1 can be written as A158250(n)^2-a(n)*(16)^2=1. LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..10000 Vincenzo Librandi, X^2-AY^2=1 E. J. Barbeau, Polynomial Excursions, Chapter 10: Diophantine equations (2010), pages 84-85 (row 15 in the first table at p. 85, case d(t) = t*(16^2*t-2)). Index to sequences with linear recurrences with constant coefficients, signature (3,-3,1). FORMULA a(n) = 3*a(n-1) -3*a(n-2) +a(n-3). G.f.: x*(-254-258*x)/(x-1)^3. MATHEMATICA LinearRecurrence[{3, -3, 1}, {254, 1020, 2298}, 50] PROG (MAGMA) I:=[254, 1020, 2298]; [n le 3 select I[n] else 3*Self(n-1)-3*Self(n-2)+1*Self(n-3): n in [1..50]]; (PARI) a(n) = 256*n^2-2*n. CROSSREFS Cf. A158250. Sequence in context: A144855 A110827 A062664 * A196738 A195859 A145715 Adjacent sequences:  A158246 A158247 A158248 * A158250 A158251 A158252 KEYWORD nonn,easy AUTHOR Vincenzo Librandi, Mar 15 2009 STATUS approved

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