A153877 Numbers n such that 5n-1 and 5n+1 are both prime.

6, 12, 30, 36, 48, 54, 84, 114, 120, 132, 162, 204, 210, 246, 258, 264, 324, 390, 426, 462, 468, 510, 546, 558, 594, 600, 624, 660, 666, 672, 678, 708, 786, 804, 810, 846, 852, 930, 960, 1002, 1020, 1056, 1104, 1128, 1170, 1176, 1218, 1254, 1260, 1272

Offset: 1

Author

Vincenzo Librandi, Jan 03 2009

Keywords

• nonn
• easy

Comments

a(n) is an integer multiple of 6. - Alois P. Heinz, Jan 04 2009

Examples

			n=6, 5n-1=29, 5n+1=31; n=30, 5n-1=149, 5n+1=151.
		

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A153355, A153088.

Programs

Magma

[ n: n in [0..2000] | IsPrime(5*n-1) and IsPrime(5*n+1)]; // Vincenzo Librandi, Jul 31 2012

Maple

a:= proc(n::posint) option remember; local m; if n=1 then 6 else for m from a(n-1)+6 by 6 while not (isprime(5*m-1) and isprime(5*m+1)) do od; m fi end: seq(a(n), n=1..100); # Alois P. Heinz, Jan 04 2009

Mathematica

Select[Range[0,100001],PrimeQ[5#-1]&& PrimeQ[5#+1]&] (* Vincenzo Librandi, Jul 31 2012 *)

Extensions

Corrected and extended by Alois P. Heinz and R. J. Mathar, Jan 04 2009