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Primes p such that p + ceiling(sqrt(p)) is also prime.
2

%I #15 Aug 17 2019 17:04:14

%S 3,13,31,53,59,97,127,137,139,179,241,293,313,389,457,547,563,569,647,

%T 733,769,853,857,877,881,977,1019,1117,1129,1153,1283,1291,1409,1433,

%U 1531,1543,1567,1579,1597,1699,1741,1747,1759,1889,1907,2053,2083,2221

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

%H Charles R Greathouse IV, <a href="/A145907/b145907.txt">Table of n, a(n) for n = 1..10000</a>

%e For p = 13; 13 + ceiling(sqrt(13)) = 17, which is prime.

%t Select[Prime[Range[400]],PrimeQ[#+Ceiling[Sqrt[#]]]&] (* _Harvey P. Dale_, Aug 17 2019 *)

%o (PARI) isok(n) = isprime(n) && isprime(n + sqrtint(n) + 1); \\ _Michel Marcus_, Aug 15 2013

%Y Cf. A086085, A145908.

%K nonn

%O 1,1

%A _Kyle D. Balliet_, Oct 24 2008, Nov 06 2008

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