"Email this user" was broken Aug 14 to 9am Aug 16. If you sent someone a message in this period, please send it again.

1,1

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