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A243154 Smallest k>=0 such that prime(n)*prime(n+k)-2 is prime. 3
0, 0, 0, 0, 4, 0, 2, 0, 4, 0, 7, 0, 4, 0, 0, 4, 11, 0, 2, 0, 4, 7, 7, 0, 12, 4, 0, 0, 2, 9, 0, 0, 2, 0, 6, 2, 1, 4, 10, 0, 13, 4, 0, 4, 10, 4, 0, 0, 2, 8, 0, 0, 5, 6, 0, 30, 20, 16, 4, 11, 7, 0, 5, 13, 0, 11, 18, 0, 2, 18, 5, 0, 1, 4, 5, 10, 4, 7, 4, 5, 11 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,5

COMMENTS

One of the possible illustrations of Chen's theorem: there are infinitely many primes p such that p+2 is semiprime.

For a dual sequence, see A243158.

LINKS

Table of n, a(n) for n=1..81.

PROG

(PARI) vector(1000, n, k=0; while(!isprime(prime(n)*prime(n+k)-2), k++); k) \\ Colin Barker, May 31 2014

CROSSREFS

Cf. A243158.

Sequence in context: A280639 A319037 A067565 * A307717 A226782 A010635

Adjacent sequences:  A243151 A243152 A243153 * A243155 A243156 A243157

KEYWORD

nonn

AUTHOR

Vladimir Shevelev, May 31 2014

EXTENSIONS

a(25) corrected and more terms from Colin Barker, May 31 2014

STATUS

approved

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Last modified July 4 16:24 EDT 2020. Contains 335448 sequences. (Running on oeis4.)