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Search: id:A102644
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| A102644 |
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A006530(x)=2 is a local minimum if x=2^n. Running downward with argument x started at 2^n, the largest prime divisor should increase. The value of first peak is a(n). |
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+0
5
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| 2, 3, 7, 13, 31, 61, 127, 127, 73, 1021, 89, 4093, 8191, 16381, 151, 257, 131071, 131071, 524287, 1048573, 337, 683, 178481, 16777213, 1801, 8191, 262657, 1877171, 2089, 46684427, 2147483647, 2147483647, 599479, 3360037, 6871947673, 283007
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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We may call these terms "downward-zenith-primes" belonging to 2^n-s. They do not exceed previous-primes before 2^n [A0014234(n)].
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EXAMPLE
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n=20: 2^20=1048576; the largest prime divisors for arguments if running downward from 2^20 are as follows: {2,41,524287,1048573,73}.
The first lower peak before argument 2^20=1048576 is a(20)=1048573.
n=1: a(1)=2 the peak equals the central value because there are no prime divisors>0 below n=2^1=2.
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CROSSREFS
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Cf. A006530, A102640, A102641, A102642, A102643, A014234.
Sequence in context: A070218 A048456 A071899 this_sequence A014234 A124430 A002013
Adjacent sequences: A102641 A102642 A102643 this_sequence A102645 A102646 A102647
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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), Jan 21 2005
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