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Search: id:A089819
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| A089819 |
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Number of subsets of {1,.., n} containing no primes. |
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+0
5
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| 2, 2, 2, 4, 4, 8, 8, 16, 32, 64, 64, 128, 128, 256, 512, 1024, 1024, 2048, 2048, 4096, 8192, 16384, 16384, 32768, 65536, 131072, 262144, 524288, 524288, 1048576, 1048576, 2097152, 4194304, 8388608, 16777216, 33554432, 33554432, 67108864
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OFFSET
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1,1
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COMMENT
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a(n) = Product(2-A010051(k): 1<=k<=n) = A089818(n,0) = A000079(n) - A089820(n).
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FORMULA
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a(n) = 2^(n-pi(n)), with pi = A000720.
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EXAMPLE
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a(6)=8 subsets of {1,2,3,4,5,6} contain no prime: {1,4,6}, {4,6},
{1,6}, {1,4}, {6}, {4}, {1}, and the empty set.
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CROSSREFS
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Cf. A089821, A089822.
Sequence in context: A097196 A132325 A010238 this_sequence A059888 A024681 A007495
Adjacent sequences: A089816 A089817 A089818 this_sequence A089820 A089821 A089822
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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), Nov 12 2003
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