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 A171581 The natural numbers without primes > 3. 3
 1, 2, 3, 4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 22, 24, 25, 26, 27, 28, 30, 32, 33, 34, 35, 36, 38, 39, 40, 42, 44, 45, 46, 48, 49, 50, 51, 52, 54, 55, 56, 57, 58, 60, 62, 63, 64, 65, 66, 68, 69, 70, 72, 74, 75, 76, 77, 78, 80, 81, 82, 84, 85, 86, 87, 88, 90, 91, 92, 93, 94 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS 1, 2, 3 and the composites A002808. LINKS MATHEMATICA With[{nn=100}, Join[{1, 2, 3}, Complement[Range[4, nn], Prime[Range[ PrimePi[ nn]]]]]] (* Harvey P. Dale, Nov 18 2013 *) PROG (PARI) is(n)=if(n<5, n>0, !isprime(n)) \\ Charles R Greathouse IV, Nov 13 2015 CROSSREFS Sequence in context: A153276 A108408 A173905 * A063450 A047229 A094229 Adjacent sequences:  A171578 A171579 A171580 * A171582 A171583 A171584 KEYWORD nonn,easy,less AUTHOR Juri-Stepan Gerasimov, Dec 12 2009, Dec 15 2009 STATUS approved

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