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A143860
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Ulam's spiral (NNW spoke).
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2
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1, 16, 63, 142, 253, 396, 571, 778, 1017, 1288, 1591, 1926, 2293, 2692, 3123, 3586, 4081, 4608, 5167, 5758, 6381, 7036, 7723, 8442, 9193, 9976, 10791, 11638, 12517, 13428, 14371, 15346, 16353, 17392, 18463, 19566, 20701, 21868, 23067, 24298
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OFFSET
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1,2
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COMMENTS
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Also, except for the first term, sequence found by reading the line from 16, in the direction 16, 63,... in the square spiral whose vertices are the generalized decagonal numbers A074377. - Omar E. Pol, Nov 05 2012
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LINKS
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Vincenzo Librandi, Table of n, a(n) for n = 1..1000
Index to sequences with linear recurrences with constant coefficients, signature (3,-3,1).
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FORMULA
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a(n) = 16*n^2-33*n+18. [From R. J. Mathar, Sep 08 2008]
G.f. x*(1+13*x+18*x^2) / (1-x)^3 . - R. J. Mathar, Oct 31 2011
a(n) = 3*a(n-1) -3*a(n-2) +a(n-3). - Vincenzo Librandi, Jul 10 2012
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MATHEMATICA
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f[n_] := 16n^2 -33n +18; Array[f, 40] (* Robert G. Wilson v, Oct 31 2011 *)
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PROG
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(MAGMA) [16*n^2-33*n+18: n in [1..40]]; // Vincenzo Librandi, Jul 10 2012
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CROSSREFS
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Sequence in context: A118254 A066391 A022289 * A100176 A060091 A076751
Adjacent sequences: A143857 A143858 A143859 * A143861 A143862 A143863
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KEYWORD
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nonn,easy
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AUTHOR
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Vladimir Joseph Stephan Orlovsky, Sep 03 2008
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STATUS
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approved
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