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Search: id:A154274
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| A154274 |
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Primes of the form: nonprime(prime(n))-(-1)^n. |
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+0
1
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| 2, 3, 17, 19, 71, 97, 127, 131, 139, 191, 193, 227, 229, 251, 281, 337, 349, 353, 389, 443, 503, 541, 557, 563, 571, 613, 659, 701, 719, 727, 743, 877, 911, 971, 1031, 1087, 1091, 1103, 1217, 1297, 1301, 1409, 1439, 1451, 1481, 1531, 1549, 1657, 1697, 1741
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Where n-th "prime nonprime" = A141468(A000040(n))) and 1-th "prime nonprime" = 0.
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EXAMPLE
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If n=1 and nonprime(prime(1))-(-1)^1=nonprime(2)+1=1+1=2(prime), then 2=a(1). If n=2 and nonprime(prime(2))-(-1)^2=nonprime(3)-1=4-1=3(prime), then 3=a(2). If n=3, then nonprime(prime(3))-(-1)^3=nonprime(5)+1=8+1=9(composite). If n=4, then nonprime(prime(4))-(-1)^4=nonprime(7)-1=10-1=9(composite). If n=5 and nonprime(prime(5))-(-1)^5=nonprime(11)+1=16+1=17(prime), then 17=a(3), etc.
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MAPLE
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A141468 := proc(n) if n <= 2 then n-1 ; else for a from procname(n-1)+1 do if not isprime(a) then RETURN(a) ; fi; od; fi: end: for n from 1 to 400 do p := A141468(ithprime(n))-(-1)^n ; if isprime(p) then printf("%d, ", p); fi; od: [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 14 2009]
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CROSSREFS
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Cf. A000040, A141468.
Sequence in context: A135931 A051074 A051094 this_sequence A140834 A121409 A041295
Adjacent sequences: A154271 A154272 A154273 this_sequence A154275 A154276 A154277
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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), Jan 06 2009
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EXTENSIONS
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Corrected and extended by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 14 2009
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