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Cf. A063643 Primes p such that p+/-2 are semiprimes, A117328 Primes p such that p+/-4 are semiprimes.
Table of n, a(n) for n=1..55.
a(100)=571 because 571-2*100=371=7*53 (semiprime), 571+2*100=771=3*257 (semiprime).
Cf. A063643.
Sequence in context: A157677 A092518 A110584 * A180538 A227217 A229176
Adjacent sequences: A115393 A115394 A115395 * A115397 A115398 A115399
nonn
Zak Seidov, Mar 08 2006
approved