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Search: id:A056673
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| A056673 |
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Number of unitary and square-free divisors of C(n,[n/2]). Also the number of divisors of special square-free part of A001405(n), A0560600(n). |
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+0
1
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| 1, 2, 2, 4, 4, 2, 4, 8, 4, 2, 16, 8, 8, 8, 8, 16, 32, 16, 32, 16, 32, 32, 64, 32, 16, 16, 8, 8, 32, 32, 64, 128, 128, 64, 256, 128, 128, 128, 512, 256, 512, 512, 512, 512, 64, 64, 256, 128, 128, 128, 128, 128, 256, 256, 2048, 2048, 4096, 4096, 2048, 2048, 2048, 2048
(list; graph; listen)
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OFFSET
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1,2
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FORMULA
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a(n)=A000005[A055231(x)]=A000005[A007913(x)/A055229(x)], where x=A001405(n)=C(n, [n/2])
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EXAMPLE
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n=14, C(15,7)=3432=2.2.2.3.11.13, it has 32 divisors, 16 unitary and 16 square-free divisors. Only 6 ones belong to both classes: {1,3,11,13,33,39,143,429}, so a(14)=8.
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CROSSREFS
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A000005, A055231, A000005, A007913, A055229, A001405, A056060.
Sequence in context: A065176 A060267 A048244 this_sequence A128442 A038674 A090277
Adjacent sequences: A056670 A056671 A056672 this_sequence A056674 A056675 A056676
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Aug 10 2000
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