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Search: id:A100821
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| A100821 |
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a(n) = 1 if prime(n) + 2 = prime(n+1), otherwise 0. |
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+0
2
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| 0, 1, 1, 0, 1, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Same as A062301 except for starting point.
a(n)=1 iff prime(n) is the smaller of a pair of twin primes, else a(n)=0. This sequence can be derived from the sequence b(n)=1 iff n and n+2 are both prime, else b(n)=0. This latter sequence has as its inverse Moebius transform the sequence c(n) = the number of distinct factors of n which are the smaller of a pair of twin primes. For example, c(15)=2 because 15 is divisible by 3 and 5, each of which is the smaller of a pair of twin primes. - Jonathan Vos Post (jvospost2(AT)yahoo.com), Jan 07 2005
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FORMULA
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a(n) = A062301(n+1) = 1 - A100810(n).
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MATHEMATICA
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Table[If[Prime[n] + 2 == Prime[n + 1], 1, 0], {n, 120}] (Ray Chandler)
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CROSSREFS
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Adjacent sequences: A100818 A100819 A100820 this_sequence A100822 A100823 A100824
Sequence in context: A129950 A010051 A131929 this_sequence A073070 A099104 A048820
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KEYWORD
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easy,nonn
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AUTHOR
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Giovanni Teofilatto (g.teofilatto(AT)tiscalinet.it), Jan 06 2005
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EXTENSIONS
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Corrected and extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Jan 09 2005
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