login
Primes p such that p + floor(sqrt(p)) is prime.
5

%I #13 Aug 24 2024 18:16:56

%S 2,5,19,37,41,47,71,103,151,167,197,277,331,349,401,419,487,499,577,

%T 593,607,617,619,683,701,811,829,907,911,937,941,947,953,1031,1061,

%U 1451,1493,1511,1627,1657,1669,1789,1831,1847,1949,1973,2161,2309,2333,2341

%N Primes p such that p + floor(sqrt(p)) is prime.

%e a(3)=19 because 19 is prime and 19 + floor(sqrt(19)) = 19 + floor(4.358898944) = 19 + 4 = 23, which is prime.

%t f[n_]:=Floor[Sqrt[n]]+n;lst={};Do[p=Prime[n];If[PrimeQ[f[p]],AppendTo[lst,p]],{n,7!}];lst (* _Vladimir Joseph Stephan Orlovsky_, Feb 25 2010 *)

%K nonn

%O 1,1

%A Chuck Seggelin (barkeep(AT)plastereddragon.com), Jul 08 2003

%E More terms from _R. J. Mathar_, Oct 31 2008