The OEIS Foundation is grateful to everyone who made a donation during our Annual Appeal. Visit the new and spectacular Pictures from the OEIS page!
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).
Sequence in context: A157677 A092518 A110584 * A180538 A227217 A229176
Adjacent sequences: A115393 A115394 A115395 * A115397 A115398 A115399
Zak Seidov, Mar 08 2006