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A133555
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Order of A113709(n) among composite positive integers.
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1
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1, 2, 3, 6, 9, 10, 11, 14, 19, 24, 27, 28, 29, 32, 37, 42, 47, 48, 51, 56, 57, 60, 71, 74, 75, 76, 79, 82, 95, 96, 99, 104, 105, 114, 119, 124, 125, 128, 133, 138, 147, 148, 151, 152, 157, 168, 175, 178, 181, 182, 187, 196, 197, 202, 207, 212, 217, 220, 221, 228, 231
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OFFSET
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2,2
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LINKS
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FORMULA
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EXAMPLE
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The 10th prime - the 9th prime = 29-23 = 6. The integer between 23 and 29 that is divisible by 6 is 24. 24 is the 14th composite, so a(9) = 14.
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MAPLE
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A113709 := proc(n) local d, a ; d := ithprime(n+1)-ithprime(n) ; for a from ithprime(n)+1 do if a mod d = 0 then RETURN(a) ; fi ; od: end: A066246 := proc(n) local a, i; if n = 1 or isprime(n) then 0 ; else a := 0 ; for i from 4 to n do if not isprime(i) then a := a+1 ; fi ; od: RETURN(a) ; fi ; end: A133555 := proc(n) A066246(A113709(n)) ; end: seq(A133555(n), n=2..80) ; # R. J. Mathar, Jan 12 2008
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MATHEMATICA
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compositePi[n_] := n - PrimePi[n] - 1;
a[n_] := Module[{p1 = Prime[n], p2 = Prime[n+1], c}, c = SelectFirst[ Range[p1+1, p2-1], Divisible[#, p2-p1]&]; compositePi[c]];
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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