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A172409
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Numbers n such that neither n-2 nor n-3 is prime.
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0
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0, 1, 2, 3, 11, 12, 17, 18, 23, 24, 27, 28, 29, 30, 35, 36, 37, 38, 41, 42, 47, 48, 51, 52, 53, 54, 57, 58, 59, 60, 65, 66, 67, 68, 71, 72, 77, 78, 79, 80, 83, 84, 87, 88, 89, 90, 93, 94, 95, 96, 97, 98, 101, 102, 107, 108, 113, 114, 117, 118, 119, 120, 121, 122, 123, 124
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OFFSET
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1,3
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LINKS
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FORMULA
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EXAMPLE
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a(1)=0 because 0-2=-2 and 0-3=-1 are nonprime.
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MATHEMATICA
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Join[{0, 1}, Select[Range[150], !PrimeQ[#-2]&&!PrimeQ[#-3]&]] (* 0 and 1 are in the sequence because primes are usually defined to include only positive integers, but because Mathematica treats many negative numbers, including -2 and -3, as primes, it is necessary to include 0 and 1 via "Join". *) (* Harvey P. Dale, Aug 06 2012 *)
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PROG
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CROSSREFS
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KEYWORD
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nonn,easy,less
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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