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Search: id:A139636
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| A139636 |
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If n = the kth prime, then a(n) = the (k+1)th prime. If n = the kth composite, then a(n) = the (k+1)th composite. |
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+0
2
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| 3, 5, 6, 7, 8, 11, 9, 10, 12, 13, 14, 17, 15, 16, 18, 19, 20, 23, 21, 22, 24, 29, 25, 26, 27, 28, 30, 31, 32, 37, 33, 34, 35, 36, 38, 41, 39, 40, 42, 43, 44, 47, 45, 46, 48, 53, 49, 50, 51, 52, 54, 59, 55, 56, 57, 58, 60, 61, 62, 67, 63, 64, 65, 66, 68, 71, 69, 70, 72, 73, 74
(list; graph; listen)
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OFFSET
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2,1
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COMMENT
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This is a permutation of the positive integers sans 1,2,4.
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MAPLE
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A000040 := proc(n) ithprime(n) ; end: A002808 := proc(n) local a; if n = 1 then 4; else for a from A002808(n-1)+1 do if not isprime(a) then RETURN(a) ; fi ; od: fi ; end: A066246 := proc(n) local k ; if isprime(n) then 0 ; else for k from 1 do if A002808(k) = n then RETURN(k) ; fi ; od: fi ; end: A049084 := proc(n) if not isprime(n) then 0; else numtheory[pi](n) ; fi ; end: A139636 := proc(n) local k; if isprime(n) then k := A049084(n) ; RETURN(A000040(k+1)) ; else k := A066246(n) ; RETURN(A002808(k+1)) ; fi ; end: seq(A139636(n), n=2..160) ; - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 12 2008
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CROSSREFS
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Cf. A139637.
Adjacent sequences: A139633 A139634 A139635 this_sequence A139637 A139638 A139639
Sequence in context: A039041 A079253 A076054 this_sequence A047583 A138343 A010906
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet (qq-quet(AT)mindspring.com), Apr 28 2008
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 12 2008
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