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Search: id:A142346
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| A142346 |
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Primes of the form (p(n)+r(n))/2, where p(n)=n-th prime and r(n)=n-th nonprime. |
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+0
1
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| 2, 11, 47, 73, 131, 151, 173, 181, 227, 239, 271, 307, 367, 379, 383, 461, 523, 643, 661, 677, 743, 797, 991, 997, 1021, 1063, 1091, 1307, 1459, 1567, 1637, 1723, 1811, 1831, 1951, 1987, 1999, 2027, 2111, 2251, 2273, 2297, 2543, 2609, 2647, 2699, 2707, 2801
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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If n=2, then (p(2)+r(2))/2=(3+1)/2=2=a(1).
If n=6, then (p(6)+r(6))/2=(13+9)/2=11=a(2).
If n=19, then (p(19)+r(19))/2=(67+27)/2=47=a(3).
If n=28, then (p(28)+r(28))/2=(107+39)/2=73=a(4).
If n=46, then (p(46)+r(46))/2=(199+63)/2=131=a(5), etc.
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MAPLE
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A141468 := proc(n) option remember ; if n = 1 then 0; else for a from procname(n-1)+1 do if not isprime(a) then RETURN(a) ; fi; od: fi: end: A000040 := proc(n) ithprime(n) ; end: for n from 1 to 3000 do c := A000040(n)+A141468(n) ; if c mod 2 = 0 then if isprime(c/2) then printf("%d, ", c/2) ; fi; fi; od: [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 03 2008]
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CROSSREFS
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Cf. A000040, A141468.
Sequence in context: A000176 A042927 A140305 this_sequence A106980 A089682 A050929
Adjacent sequences: A142343 A142344 A142345 this_sequence A142347 A142348 A142349
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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), Sep 19 2008
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EXTENSIONS
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239 inserted, 367 inserted and extended by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 03 2008
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