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 A154376 a(n) = 25*n^2 - 2*n. 3
 23, 96, 219, 392, 615, 888, 1211, 1584, 2007, 2480, 3003, 3576, 4199, 4872, 5595, 6368, 7191, 8064, 8987, 9960, 10983, 12056, 13179, 14352, 15575, 16848, 18171, 19544, 20967, 22440, 23963, 25536, 27159, 28832, 30555, 32328, 34151, 36024 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The identity (1250*n^2 - 100*n + 1)^2 - (25*n^2 - 2*n)*(250*n - 10)^2 = 1 can be written as A154374(n)^2 - a(n)*A154378(n)^2 = 1 (see also the second comment in A154374). - Vincenzo Librandi, Jan 30 2012 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..10000 Index entries for linear recurrences with constant coefficients, signature (3,-3,1). FORMULA From Vincenzo Librandi, Jan 30 2012: (Start) G.f.: x*(23 + 27*x)/(1-x)^3. a(n) = 3*a(n-1) -3*a(n-2) +a(n-3). (End) E.g.f.: (25*x^2 + 23*x)*exp(x). - G. C. Greubel, Sep 15 2016 MATHEMATICA LinearRecurrence[{3, -3, 1}, {23, 96, 219}, 50] (* Vincenzo Librandi, Jan 30 2012 *) PROG (PARI) a(n)=25*n^2-2*n \\ Charles R Greathouse IV, Dec 26 2011 CROSSREFS Cf. A154374, A154378. Sequence in context: A257976 A183011 A158544 * A155815 A231453 A142132 Adjacent sequences:  A154373 A154374 A154375 * A154377 A154378 A154379 KEYWORD nonn,easy AUTHOR Vincenzo Librandi, Jan 08 2009 STATUS approved

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Last modified July 21 05:11 EDT 2019. Contains 325189 sequences. (Running on oeis4.)