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 A136392 6n^2 - 10n + 5. 5
 1, 9, 29, 61, 105, 161, 229, 309, 401, 505, 621, 749, 889, 1041, 1205, 1381, 1569, 1769, 1981, 2205, 2441, 2689, 2949, 3221, 3505, 3801, 4109, 4429, 4761, 5105, 5461, 5829, 6209, 6601, 7005, 7421, 7849, 8289, 8741, 9205, 9681, 10169 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Binomial transform of [1, 8, 12, 0, 0, 0,...]. Numbers n where 6n-5 is a square of a number type 6n-5, contained in A199859. [Eleonora Echeverri-Toro, Nov 29 2011] Central terms of the triangle A033292. [Reinhard Zumkeller, Feb 06 2012] Sequence found by reading the line from 1, in the direction 1, 9,..., in the square spiral whose vertices are the generalized pentagonal numbers A001318. [Omar E. Pol, Jul 18 2012] LINKS Index to sequences with linear recurrences with constant coefficients, signature (3,-3,1). FORMULA a(n) = n*(3n-2) + (n-1)*(3n-5), n>1. a(n) = n*A016777(n-1) + (n-1)*A016777(n-2). a(n) = a(n-1)+12*n-16 (with a(1)=1). [Vincenzo Librandi, Nov 24 2010] G.f.: x*(1+x)*(1+5*x)/(1-x)^3. - Colin Barker, Jan 09 2012 a(n) = 1 + A033580(n-1). - Omar E. Pol, Jul 18 2012 a(n) = A059722(n) - A059722(n-1). - J. M. Bergot, Nov 02 2012 PROG (PARI) a(n)=6*n^2-10*n+5 \\ Charles R Greathouse IV, Nov 29 2011 (Haskell) a136392 n = 2 * n * (3*n - 5) + 5 -- Reinhard Zumkeller, Feb 06 2012 CROSSREFS Cf. A016777, A201279, A204675. Sequence in context: A031296 A146869 A129397 * A162263 A055195 A024922 Adjacent sequences:  A136389 A136390 A136391 * A136393 A136394 A136395 KEYWORD nonn,easy,changed AUTHOR Gary W. Adamson, Dec 28 2007 STATUS approved

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