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 A256389 Numbers n such that one or more primes can be the arithmetic mean of 2 semiprimes whose difference is 2*n. 2
 1, 2, 3, 4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 22, 24, 26, 27, 28, 30, 32, 34, 36, 38, 39, 40, 42, 44, 46, 48, 50, 52, 54, 56, 57, 58, 60, 62, 64, 66, 68, 69, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 99, 100, 102, 104, 105, 106, 108, 110 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS That is, there are several primes p, such that p+n and p-n are both semiprime. Complement of A256387. The terms of this sequence that do not belong to A256388 are even. LINKS Table of n, a(n) for n=1..65. EXAMPLE A256381 is the list of numbers n such that n-3 and n+3 are semiprimes, and it contains a single prime, hence 3 is in the sequence. A256382 is the list of numbers n such that n-4 and n+4 are semiprimes, and it contains several primes, hence 4 is in the sequence. CROSSREFS Cf. A124936, A105571, A256382. Cf. A256387 (no prime), A256388 (a single prime). Sequence in context: A246352 A363227 A225730 * A225729 A035033 A054219 Adjacent sequences: A256386 A256387 A256388 * A256390 A256391 A256392 KEYWORD nonn AUTHOR Michel Marcus, Mar 27 2015 STATUS approved

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Last modified August 11 23:45 EDT 2024. Contains 375082 sequences. (Running on oeis4.)