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A081275
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Shallow diagonal of triangular spiral in A051682.
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2
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1, 31, 97, 199, 337, 511, 721, 967, 1249, 1567, 1921, 2311, 2737, 3199, 3697, 4231, 4801, 5407, 6049, 6727, 7441, 8191, 8977, 9799, 10657, 11551, 12481, 13447, 14449, 15487, 16561, 17671, 18817, 19999, 21217, 22471, 23761, 25087, 26449, 27847
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OFFSET
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0,2
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COMMENTS
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Binomial transform of (1, 30, 36, 0, 0, 0, .....).
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LINKS
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FORMULA
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a(n) = C(n, 0) + 30*C(n, 1) + 36*C(n, 2).
a(n) = 18*n^2+12*n+1.
G.f.: (1+28*x+7*x^2)/(1-x)^3.
a(0)=1, a(1)=31, a(2)=97, a(n)=3*a(n-1)-3*a(n-2)+a(n-3). - Harvey P. Dale, Jun 30 2011
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MATHEMATICA
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Table[30Binomial[n, 1]+36Binomial[n, 2]+1, {n, 0, 40}] (* or *) LinearRecurrence[{3, -3, 1}, {1, 31, 97}, 40] (* Harvey P. Dale, Jun 30 2011 *)
CoefficientList[Series[(1 + 28 x + 7 x^2) / (1 - x)^3, {x, 0, 40}], x] (* Vincenzo Librandi, Aug 07 2013 *)
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PROG
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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