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A056676
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Number of non-unitary but squarefree divisors of C(n,[n/2]). Also number of non-squarefree but unitary divisors of C(n,[n/2]).
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0
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0, 0, 0, 0, 0, 2, 0, 0, 4, 6, 0, 8, 8, 8, 8, 16, 0, 16, 0, 16, 32, 32, 0, 32, 48, 48, 56, 56, 96, 96, 64, 128, 128, 192, 256, 384, 384, 384, 512, 768, 512, 512, 512, 512, 448, 448, 768, 896, 896, 896, 896, 896, 768, 768, 2048, 2048, 4096, 4096, 2048, 2048, 2048, 2048
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OFFSET
| 1,6
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FORMULA
| a(n)=A039593(n)-A000005[A055231(x)] =A039593(n)-A000005[A007913(x)/A055229(x)], where x=A001405(n)=C(n, [n/2])
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EXAMPLE
| n=14, C(14,7)=3432,has 32 divisors,16 unitary,16 squarefree. The size of overlap is 8. The complementary parts are: non-unitary/squarefree set={2,6,22,26,66,78,286,828}, while the unitary/not squarefree set of equal size is: {8,24,88,104,264,312,1144,3432}.So a(14)=8.
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CROSSREFS
| A039593, A000005, A055231, A007913, A055229, A001405.
Sequence in context: A117434 A115179 A131742 * A098699 A021837 A155719
Adjacent sequences: A056673 A056674 A056675 * A056677 A056678 A056679
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), Aug 10 2000
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