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Search: id:A100319
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| A100319 |
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Even numbers n such that at least one of n-1 and n+1 is composite. |
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+0
2
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| 8, 10, 14, 16, 20, 22, 24, 26, 28, 32, 34, 36, 38, 40, 44, 46, 48, 50, 52, 54, 56, 58, 62, 64, 66, 68, 70, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100, 104, 106, 110, 112, 114, 116, 118, 120, 122, 124, 126, 128, 130, 132, 134, 136, 140, 142, 144, 146, 148
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Subsequence of A100318. For each k >= 0, a(k+1) = a(k) + 2 unless a(k) + 1 and a(k) + 3 are twin primes, in which case a(k+1) = a(k) + 4 (as a(k) - 1 and a(k) + 5 are divisible by 3).
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PROGRAM
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(PARI) forstep(n=4, 300, 2, if(isprime(n-1)+isprime(n+1)<=1, print1(n, ", ")))
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CROSSREFS
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Cf. A100318 (supersequence containing odd and even n), A045718 (n such that at least one of n-1 and n+1 is prime).
Adjacent sequences: A100316 A100317 A100318 this_sequence A100320 A100321 A100322
Sequence in context: A102615 A030490 A076639 this_sequence A060864 A087695 A134321
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KEYWORD
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nonn
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AUTHOR
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Rick L. Shepherd (rshepherd2(AT)hotmail.com), Nov 13 2004
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