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A161703
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a(n) = (4*n^3 - 12*n^2 + 14*n + 3)/3.
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18
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1, 3, 5, 15, 41, 91, 173, 295, 465, 691, 981, 1343, 1785, 2315, 2941, 3671, 4513, 5475, 6565, 7791, 9161, 10683, 12365, 14215, 16241, 18451, 20853, 23455, 26265, 29291, 32541, 36023, 39745, 43715, 47941, 52431, 57193, 62235, 67565, 73191, 79121
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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 15:
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LINKS
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FORMULA
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a(n) = C(n,0) + 2*C(n,1) + 8*C(n,3).
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EXAMPLE
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Differences of divisors of 15 to compute the coefficients of their interpolating polynomial, see formula:
1 3 5 15
2 2 10
0 8
8
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MAPLE
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MATHEMATICA
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CoefficientList[Series[(1 - x - x^2 + 9*x^3)/(1 - x)^4, {x, 0, 50}], x] (* G. C. Greubel, Jul 16 2017 *)
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PROG
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(Magma) [(4*n^3 - 12*n^2 + 14*n + 3)/3: n in [0..50]]; // Vincenzo Librandi, Dec 27 2010
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CROSSREFS
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Cf. A000124, A000125, A000127, A002522, A005408, A006261, A016813, A058331, A080856, A086514, A161701, A161702, A161704, A161706-A161708, A161710, A161711-A161713, A161715.
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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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