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A157890
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Number of primes between exponents of successive Mersenne primes.
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0
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0, 0, 0, 1, 0, 0, 2, 6, 5, 3, 2, 66, 12, 95, 120, 10, 115, 127, 18, 593, 29, 130, 896, 180, 155, 2032, 3759, 2104, 1841, 6960, 41452, 7555, 28715
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OFFSET
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1,7
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COMMENTS
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a(6) = 0 since 17 is adjacent to 19 (exponent of 7th Mersenne prime); a(7) = 2 since 23 and 29 are between 19 and 31 (exponent of 8th Mersenne prime); a(8) = 6 since 37, 41, 43, 47, 53 and 59 are between 31 and 61 (exponent of 9th Mersenne prime)
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LINKS
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Table of n, a(n) for n=1..33.
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FORMULA
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a(n) = (PrimePi(A000043(n+1))-PrimePi(A000043(n)))-1 = (A000720(A000043(n+1))-A000720(A000043(n)))-1. [From Jonathan Vos Post, Mar 09 2009]
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CROSSREFS
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Cf. A000040, A000043, A046933
Sequence in context: A004583 A175995 A021381 * A198821 A171897 A105029
Adjacent sequences: A157887 A157888 A157889 * A157891 A157892 A157893
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KEYWORD
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nonn
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AUTHOR
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Jani Melik, Mar 08 2009, Mar 10 2009
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STATUS
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approved
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