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A136392
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6n^2 - 10n + 5.
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5
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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
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OFFSET
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1,2
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COMMENTS
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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]
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LINKS
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Table of n, a(n) for n=1..42.
Index to sequences with linear recurrences with constant coefficients, signature (3,-3,1).
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FORMULA
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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
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PROG
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(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
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CROSSREFS
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Cf. A016777, A201279, A204675.
Sequence in context: A031296 A146869 A129397 * A162263 A055195 A024922
Adjacent sequences: A136389 A136390 A136391 * A136393 A136394 A136395
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KEYWORD
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nonn,easy,changed
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AUTHOR
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Gary W. Adamson, Dec 28 2007
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STATUS
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approved
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