The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A056956 Numbers n such that 6n+1 and 6n+5 are both primes. 10
 1, 2, 3, 6, 7, 11, 13, 16, 17, 18, 21, 27, 32, 37, 38, 46, 51, 52, 58, 63, 66, 73, 76, 77, 81, 83, 102, 107, 112, 123, 126, 128, 137, 142, 143, 146, 147, 151, 156, 161, 168, 181, 182, 202, 213, 216, 217, 237, 238, 241, 247, 248, 258, 261, 263, 266, 268, 277, 282 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Note that if prime p>3 then p mod 6 = 1 or 5. LINKS M. F. Hasler, Table of n, a(n) for n = 1..5000 FORMULA a(n) = (A023200(n+1)-1)/6 = (A046132(n+1)-5)/6 = A047847(n+1)/3 a(n) = floor(A087679(n+1)/6). - M. F. Hasler, Apr 05 2017 EXAMPLE a(2)=2 since 6*2+1=13 and 6*2+5=17 are both prime. MATHEMATICA Select[Range[300], And @@ PrimeQ /@ ({1, 5} + 6#) &] (* Ray Chandler, Jun 29 2008 *) PROG (PARI) is(n)=isprime(n*6+1)&&isprime(n*6+5) \\ M. F. Hasler, Apr 05 2017 CROSSREFS Cf. A002822, A024898, A024899, A059325. Sequence in context: A113545 A056825 A070757 * A171033 A269983 A323066 Adjacent sequences:  A056953 A056954 A056955 * A056957 A056958 A056959 KEYWORD nonn AUTHOR Henry Bottomley, Jul 18 2000 EXTENSIONS Edited by N. J. A. Sloane, Nov 07 2006 STATUS approved

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

Last modified September 27 08:39 EDT 2021. Contains 347689 sequences. (Running on oeis4.)