The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A164385 Composite numbers n such that n+4 and n-4 are both prime. 1
 9, 15, 27, 33, 57, 63, 75, 93, 105, 135, 153, 177, 195, 237, 267, 273, 363, 393, 405, 435, 453, 483, 495, 567, 573, 597, 603, 657, 687, 705, 723, 747, 765, 825, 915, 933, 987, 1017, 1035, 1065, 1113, 1167, 1197, 1227, 1233, 1287, 1293, 1323, 1377, 1443, 1455, 1485 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Composite numbers of the form A023202(k)+4, any k. A087680 without the {7} [Proof: there are no 3 primes in arithmetic progression p, p+4, p+8, except p=3]. A164383 INTERSECT A164384; A087680 INTERSECT A002808. If p=3*l+1, p+8 were divisible by 3, and if p=3*l+2, p+4 were divisible by 3. - R. J. Mathar, Aug 20 2009] All terms are divisible by 3. - Zak Seidov, Apr 22 2015 LINKS Table of n, a(n) for n=1..52. FORMULA a(n) = A023202(n+1)+4 = A087680(n+1). - Zak Seidov, Apr 22 2015 EXAMPLE a(1) = 5(prime)+4 = 13(prime)-4 = 9 (composite). a(2) = 11(prime)+4 = 19(prime)-4 = 15 (composite). MATHEMATICA Select[Range[8, 2000], PrimeQ[#+4] && PrimeQ[#-4] &] (* Vincenzo Librandi, Apr 22 2015 *) PROG (Magma) [n: n in [8..2000] | IsPrime(n+4) and IsPrime(n-4)]; // Vincenzo Librandi, Apr 22 2015 CROSSREFS Cf. A002808, A023202, A087680. Sequence in context: A082549 A013569 A129401 * A339519 A258813 A046353 Adjacent sequences: A164382 A164383 A164384 * A164386 A164387 A164388 KEYWORD nonn AUTHOR Juri-Stepan Gerasimov, Aug 14 2009 EXTENSIONS 65 removed, 337 changed to 237 etc. by R. J. Mathar, Aug 20 2009 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 July 25 12:21 EDT 2024. Contains 374588 sequences. (Running on oeis4.)