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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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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; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| 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).
The even nonisolated primes(n+1). [From Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Nov 09 2009]
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FORMULA
| a(n)=A167692(n+1). [From Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Nov 09 2009]
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PROG
| (PARI) forstep(n=4, 300, 2, if(isprime(n-1)+isprime(n+1)<=1, print1(n, ", ")))
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CROSSREFS
| Cf. A100318 (supersequence containing odd and even n), A045718 (n such that at least one of n-1 and n+1 is prime).
Cf. A167692(the even nonisolated nonprimes). [From Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Nov 09 2009]
Sequence in context: A030490 A076639 * A167692 A171689 A163628 A060864
Adjacent sequences: A100316 A100317 A100318 * A100320 A100321 A100322
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KEYWORD
| nonn
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AUTHOR
| Rick L. Shepherd (rshepherd2(AT)hotmail.com), Nov 13 2004
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