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Search: id:A162309
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| A162309 |
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The count of isolated primes up to the smaller component of the n-th twin prime pair. |
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+0
1
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| 1, 1, 1, 1, 2, 3, 5, 6, 10, 10, 13, 13, 17, 17, 17, 19, 20, 23, 24, 26, 29, 39, 39, 43, 50, 54, 57, 59, 60, 62, 80, 80, 80, 82, 84, 101, 101, 102, 102, 104, 110, 119, 122, 123, 124, 125, 133, 136, 138, 138, 153, 154, 158, 159, 160, 167, 174, 174, 178, 178, 182, 185, 189, 189
(list; graph; listen)
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OFFSET
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1,5
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COMMENT
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Cardinality of the set of members of A007510 which are smaller than A001359(n).
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FORMULA
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a(n+1)-a(n) = A027833(n)-2, n>1. [R. J. Mathar, Aug 29 2009]
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EXAMPLE
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a(1)=1 counts the 2 smaller than 3. a(2)= 1 counts the {2} smaller than 5.
a(5)= 2 counts 2 and 23 smaller than 29. a(6)= 3 counts 2, 23 and 37 smaller than 41.
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MAPLE
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read("transforms3") ; tp := BFILETOLIST("b001359.txt") ;
A162309 := proc(n) global tp; a := 0 ; for j from 2 to op(n, tp)-1 do if isprime(j) then if ( j in tp ) or (j-2) in tp then ; else a :=a +1; fi; fi; od: a ; end:
seq(A162309(n), n=1..130 ); # R. J. Mathar, Aug 29 2009
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CROSSREFS
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Cf. A000040, A141468, A073425.
Sequence in context: A061939 A029503 A133139 this_sequence A014593 A034044 A047447
Adjacent sequences: A162306 A162307 A162308 this_sequence A162310 A162311 A162312
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KEYWORD
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nonn
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AUTHOR
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Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Jul 01 2009
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EXTENSIONS
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53 replaced by 54, two times 100 removed etc, R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 29 2009
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