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A080860
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10*n^2 + 5*n + 1.
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1
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1, 16, 51, 106, 181, 276, 391, 526, 681, 856, 1051, 1266, 1501, 1756, 2031, 2326, 2641, 2976, 3331, 3706, 4101, 4516, 4951, 5406, 5881, 6376, 6891, 7426, 7981, 8556, 9151, 9766, 10401, 11056, 11731, 12426, 13141, 13876, 14631, 15406, 16201, 17016, 17851
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OFFSET
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0,2
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COMMENTS
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The old definition of this sequence was "Generalized polygonal numbers".
Column T(n,5) of A080853.
Sequence found by reading the line from 1, in the direction 1, 16,..., in the square spiral whose vertices are the generalized heptagonal numbers A085787. - Omar E. Pol, Sep 10 2011
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LINKS
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Table of n, a(n) for n=0..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) = C(5,0) + C(5,1)*n + C(5,2)*n^2.
G.f. (C(4,0) + (C(6,2)-2)*x + C(4,2)*x^2)/(1-x)^3 = (1+13*x+6*x^2)/(1-x)^3
a(n) = 20*n+a(n-1)-5 with n>0, a(0)=1. [Vincenzo Librandi, Aug 08 2010]
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CROSSREFS
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Sequence in context: A221485 A204723 A204962 * A204716 A192248 A044118
Adjacent sequences: A080857 A080858 A080859 * A080861 A080862 A080863
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KEYWORD
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nonn,easy
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AUTHOR
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Paul Barry, Feb 23 2003
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EXTENSIONS
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Definition replaced with the closed form by Bruno Berselli, Jan 16 2013
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STATUS
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approved
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