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A304250
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Perfect powers whose prime factors span an initial interval of prime numbers.
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3
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4, 8, 16, 32, 36, 64, 128, 144, 216, 256, 324, 512, 576, 900, 1024, 1296, 1728, 2048, 2304, 2916, 3600, 4096, 5184, 5832, 7776, 8100, 8192, 9216, 11664, 13824, 14400, 16384, 20736, 22500, 26244, 27000, 32400, 32768, 36864, 44100, 46656, 57600, 65536, 72900
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OFFSET
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1,1
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COMMENTS
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The multiset of prime indices of a(n) is the a(n)-th row of A112798. This multiset is normal, meaning it spans an initial interval of positive integers, and periodic, meaning its multiplicities have a common divisor greater than 1.
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LINKS
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FORMULA
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EXAMPLE
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Sequence of all normal periodic multisets begins
4: {1,1}
8: {1,1,1}
16: {1,1,1,1}
32: {1,1,1,1,1}
36: {1,1,2,2}
64: {1,1,1,1,1,1}
128: {1,1,1,1,1,1,1}
144: {1,1,1,1,2,2}
216: {1,1,1,2,2,2}
256: {1,1,1,1,1,1,1,1}
324: {1,1,2,2,2,2}
512: {1,1,1,1,1,1,1,1,1}
576: {1,1,1,1,1,1,2,2}
900: {1,1,2,2,3,3}
1024: {1,1,1,1,1,1,1,1,1,1}
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MATHEMATICA
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Select[Range[1000], FactorInteger[#][[-1, 1]]==Prime[Length[FactorInteger[#]]]&&GCD@@FactorInteger[#][[All, 2]]>1&]
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CROSSREFS
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Cf. A000837, A000961 A001597, A007916, A018783, A052409, A052410, A055932, A056239, A112798, A178472, A303431, A303709, A304450.
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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