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 A154377 a(n) = 25*n^2 + 2*n. 4
 27, 104, 231, 408, 635, 912, 1239, 1616, 2043, 2520, 3047, 3624, 4251, 4928, 5655, 6432, 7259, 8136, 9063, 10040, 11067, 12144, 13271, 14448, 15675, 16952, 18279, 19656, 21083, 22560, 24087, 25664, 27291, 28968, 30695, 32472, 34299, 36176 (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 A154375(n)^2 - a(n)*A154379(n)^2 = 1 (see also the second comment in A154375). - 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 a(n) = 3*a(n-1) -3*a(n-2) +a(n-3). G.f.: x*(27 + 23*x)/(1-x)^3. E.g.f.: (25*x^2 + 27*x)*exp(x). - G. C. Greubel, Sep 15 2016 MATHEMATICA LinearRecurrence[{3, -3, 1}, {27, 104, 231}, 50] PROG (PARI) a(n)=25*n^2+2*n \\ Charles R Greathouse IV, Dec 23 2011 CROSSREFS Cf. A154375, A154379. Sequence in context: A256646 A323034 A031429 * A232283 A036923 A036346 Adjacent sequences:  A154374 A154375 A154376 * A154378 A154379 A154380 KEYWORD nonn,easy AUTHOR Vincenzo Librandi, Jan 08 2009 STATUS approved

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Last modified June 13 20:25 EDT 2021. Contains 345009 sequences. (Running on oeis4.)