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 A086086 Primes p such that p - floor(sqrt(p)) is prime. 6

%I #8 Sep 26 2017 12:41:06

%S 3,5,7,17,23,37,43,47,67,79,107,113,149,151,163,211,257,331,349,409,

%T 421,439,509,521,587,593,601,617,709,727,797,839,907,911,937,941,1051,

%U 1063,1163,1187,1319,1327,1447,1471,1489,1607,1619,1637,1667,1783,1789,1801

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

%H Harvey P. Dale, <a href="/A086086/b086086.txt">Table of n, a(n) for n = 1..1000</a>

%e a(5)=23 because 19 is prime and 23 - (floor(Sqrt(23)) = 23 - (floor(4.795831523)) = 23 - 4 = 19, which is prime.

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

%t Select[Prime[Range[300]],PrimeQ[#-Floor[Sqrt[#]]]&] (* _Harvey P. Dale_, Sep 26 2017 *)

%K nonn

%O 1,1

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

%E More terms from _Vladimir Joseph Stephan Orlovsky_, Feb 25 2010

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Last modified February 21 22:50 EST 2024. Contains 370239 sequences. (Running on oeis4.)