The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A137625 The initial prime in the first set of n consecutive primes for which p+4 is semiprime. 3
 2, 29, 173, 709, 1741, 8297, 8297, 19213, 175229, 175229, 33952609, 4377722623, 4377722623, 1242030992173, 1242030992173 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Suggested by Carlos Rivera's Puzzle 429 which asks for runs where p+2 is biprime. LINKS Table of n, a(n) for n=1..15. EXAMPLE a(2)=29 because this is the first prime in a run of 2 where p+4 is semiprime (3*11). PROG (UBASIC) 10 'p+4 is biprime 20 N=1 30 A=3:S=sqrt(N) 40 B=N\A: if B*A=N then N=N+2:goto 30 50 A=A+2: if A<=S then 40 60 C=C+1:O=N+4:D=prmdiv(O):E=O\D 70 if E<>prmdiv(E) or E=1 then C=0:goto 90 80 print C; N; D; E; O: if C>=10 then stop 90 N=N+2:goto 30 CROSSREFS Cf. A001358, A137626, A137627, A137628. Sequence in context: A308899 A028883 A024200 * A132412 A369384 A342454 Adjacent sequences: A137622 A137623 A137624 * A137626 A137627 A137628 KEYWORD more,nonn AUTHOR Enoch Haga, Jan 30 2008 EXTENSIONS a(1) corrected and a(11)-a(15) from Giovanni Resta, Jun 22 2018 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified June 13 10:52 EDT 2024. Contains 373387 sequences. (Running on oeis4.)