1,1

Find a run of primes where p+4 is semiprime

a(2)=31 because that is the last prime in a run of 2 where p+4 is semiprime (5*7).

Cf. A001358 A137625 A137627 A137628.

Sequence in context: A045904 A034353 A078526 this_sequence A057426 A015540 A014987

Adjacent sequences: A137623 A137624 A137625 this_sequence A137627 A137628 A137629

easy,more,nonn

Enoch Haga (Enokh(AT)comcast.net), Jan 30 2008