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A161713
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(-n^5 + 15*n^4 - 65*n^3 + 125*n^2 - 34*n + 40)/40.
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21
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1, 2, 4, 7, 14, 28, 49, 71, 79, 46, -70, -329, -812, -1624, -2897, -4793, -7507, -11270, -16352, -23065, -31766, -42860, -56803, -74105, -95333, -121114, -152138, -189161, -233008, -284576, -344837, -414841, -495719, -588686, -695044
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| {a(k): 0 <= k < 6} = divisors of 28:
a(n) = A027750(A006218(27) + k + 1), 0 <= k < A000005(28).
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LINKS
| Vincenzo Librandi, Table of n, a(n) for n = 0..10000
R. Zumkeller, Enumerations of Divisors
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FORMULA
| a(n) = C(n,0) + C(n,1) + C(n,2) + 3*C(n,4) - 3*C(n,5).
G.f.: -(-1+4*x-7*x^2+7*x^3-7*x^4+7*x^5)/(-1+x)^6. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jun 18 2009]
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EXAMPLE
| Differences of divisors of 28 to compute the coefficients of their interpolating polynomial, see formula:
1 ... 2 ... 4 ... 7 ... 14 ... 28
.. 1 ... 2 ... 3 ... 7 ... 14
..... 1 ... 1 ... 4 ... 7
........ 0 ... 3 ... 3
........... 3 ... 0
............. -3.
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PROG
| (MAGMA) [(-n^5 + 15*n^4 - 65*n^3 + 125*n^2 - 34*n + 40)/40: n in [0..40]]; // Vincenzo Librandi, Jul 17 2011
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CROSSREFS
| A005408, A000124, A016813, A086514, A000125, A058331, A002522, A161701, A161702, A161703, A000127, A161704, A161706, A161707, A161708, A161710, A080856, A161711, A161712, A161715, A006261.
A018254, A161700, A161856. [From Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Jun 21 2009]
Sequence in context: A018254 A018660 A018692 * A018330 A068060 A057744
Adjacent sequences: A161710 A161711 A161712 * A161714 A161715 A161716
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KEYWORD
| sign,easy
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AUTHOR
| Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Jun 17 2009
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