A138025 - OEIS

%I #15 Dec 04 2016 05:09:39

%S 19099919,52554569,85864769,171729539,198479579,226366139,305192579,

%T 344319029,396959159,474118349,574964129,610385159,685066979,

%U 764406059,1085182229,1126004219,1195651139,1372213439,1484454269,1573750049,2270291519,2365144079,2400025739

%N Numbers n such that n remains prime through 7 iterations of function f(x) = 2x + 1.

%C n, 2*n+1, 4*n+3, 8*n+7, 16*n+15, 32*n+31, 64*n+63, and 128*n+127 are primes. - _John Cerkan_, Dec 04 2016

%F a(n) == 29 (mod 30). - _John Cerkan_, Nov 30 2016

%t Select[Prime[Range[10^7]],PrimeQ[a1=2*#+1]&&PrimeQ[a2=2*a1+1]&&PrimeQ[a3=2*a2+1]&&PrimeQ[a4=2*a3+1]&&PrimeQ[a5=2*a4+1]&&PrimeQ[a6=2*a5+1]&&PrimeQ[a7=2*a6+1] &]

%K nonn

%O 1,1

%A _Vladimir Joseph Stephan Orlovsky_, May 01 2008

%E More terms from _Vladimir Joseph Stephan Orlovsky_, Jan 17 2009

%E a(7)-a(23) from _John Cerkan_, Nov 30 2016