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A161711
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a(n) = (-4*n^3 + 27*n^2 - 20*n + 3)/3.
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18
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1, 2, 13, 26, 33, 26, -3, -62, -159, -302, -499, -758, -1087, -1494, -1987, -2574, -3263, -4062, -4979, -6022, -7199, -8518, -9987, -11614, -13407, -15374, -17523, -19862, -22399, -25142, -28099, -31278, -34687, -38334, -42227, -46374, -50783
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OFFSET
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0,2
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COMMENTS
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{a(k): 0 <= k < 4} = divisors of 26:
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LINKS
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FORMULA
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a(n) = C(n,0) + C(n,1) + 10*C(n,2) - 8*C(n,3).
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EXAMPLE
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Differences of divisors of 26 to compute the coefficients of their interpolating polynomial, see formula:
1 2 13 26
1 11 13
10 2
-8
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MATHEMATICA
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LinearRecurrence[{4, -6, 4, -1}, {1, 2, 13, 26}, 40] (* Harvey P. Dale, Jul 02 2017 *)
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PROG
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(Magma) [(-4*n^3 + 27*n^2 - 20*n + 3)/3: n in [0..40]]; // Vincenzo Librandi, Jul 17 2011
(PARI) x='x+O('x^50); Vec((1-2*x+11*x^2-18*x^3)/(1-x)^4) \\ G. C. Greubel, Jul 16 2017
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CROSSREFS
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Cf. A005408, A000124, A016813, A086514, A000125, A058331, A002522, A161701, A161702, A161703, A000127, A161704, A161706, A161707, A161708, A161710, A080856, A161712, A161713, A161715, A006261.
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KEYWORD
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sign,easy
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AUTHOR
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STATUS
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approved
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