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A065896
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Which composite number is 2n ?
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1
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0, 1, 2, 3, 5, 6, 7, 9, 10, 11, 13, 14, 16, 18, 19, 20, 22, 24, 25, 27, 28, 29, 31, 32, 34, 36, 37, 39, 41, 42, 43, 45, 47, 48, 50, 51, 52, 54, 56, 57, 59, 60, 62, 64, 65, 67, 69, 71, 72, 74, 75, 76, 78, 79, 80, 82, 83, 85, 87, 89, 91, 93, 95, 96, 98, 99, 101, 103, 104, 105
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,3
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LINKS
| Harry J. Smith, Table of n, a(n) for n=1,...,1000
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EXAMPLE
| a[9] = 10, since 18 is the 10th composite number: 4, 6, 8, 9, 10, 12, 14, 15, 16, 18.
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MATHEMATICA
| Table[2*n-(PrimePi[2*n])-1, {n, 1, 128}]
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PROG
| (PARI) { for (n=1, 1000, f=2*n; a=f - primepi(f) - 1; write("b065896.txt", n, " ", a) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Nov 04 2009]
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CROSSREFS
| Cf. A002808, A000720, A005843
Sequence in context: A137217 A023705 A188070 * A099308 A074235 A192189
Adjacent sequences: A065893 A065894 A065895 * A065897 A065898 A065899
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), Nov 28 2001
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