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Search: id:A161707
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| A161707 |
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(4*n^3 - 9*n^2 + 11*n + 3)/3. |
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+0
22
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| 1, 3, 7, 21, 53, 111, 203, 337, 521, 763, 1071, 1453, 1917, 2471, 3123, 3881, 4753, 5747, 6871, 8133, 9541, 11103, 12827, 14721, 16793, 19051, 21503, 24157, 27021, 30103, 33411, 36953, 40737, 44771, 49063, 53621, 58453, 63567, 68971, 74673
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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{a(k): 0 <= k < 4} = divisors of 21:
a(n) = A027750(A006218(20) + k + 1), 0 <= k < A000005(21).
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LINKS
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R. Zumkeller, Enumerations of Divisors
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FORMULA
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a(n) = C(n,0) + 2*C(n,1) + 2*C(n,2) + 8*C(n,3).
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EXAMPLE
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Differences of divisors of 21 to compute the coefficients of their interpolating polynomial, see formula:
1 ... 3 ... 7 ... 21
.. 2 ... 4 .. 14
..... 2 .. 10
........ 8.
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CROSSREFS
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A005408, A000124, A016813, A086514, A000125, A058331, A002522, A161701, A161702, A161703, A000127, A161704, A161706, A161708, A161710, A080856, A161711, A161712, A161713, A161715, A006261.
Sequence in context: A036569 A018303 A098545 this_sequence A151267 A091489 A047087
Adjacent sequences: A161704 A161705 A161706 this_sequence A161708 A161709 A161710
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KEYWORD
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nonn
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AUTHOR
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Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Jun 17 2009
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