A224796 - OEIS

%I #27 Oct 10 2024 19:33:50

%S 1,4,6,10,13,15,17,25,31,32,34,36,48,50,52,53,55,57,71,73,76,80,90,99,

%T 101,111,122,134,141,143,155,160,162,174,181,187,195,197,201,204,206,

%U 208,220,223,229,239,241,246,258,262,264,267,279,281,290,309,311,313

%N Pi*n rounded to the nearest integer is prime.

%H Charles R Greathouse IV, <a href="/A224796/b224796.txt">Table of n, a(n) for n = 1..10000</a>

%H Chris Caldwell and G. L. Honaker, Jr., <a href="https://t5k.org/curios/page.php?curio_id=25961">Prime curio for 15</a>

%e a(3)=6 because Pi*6 = 18.849559..., which rounds to 19 (a prime number).

%t Select[Range[350],PrimeQ[Round[Pi #]]&] (* _Harvey P. Dale_, Oct 10 2024 *)

%o (PARI) is(n)=isprime(round(Pi*n)) \\ _Charles R Greathouse IV_, Apr 18 2013

%Y Cf. A000040, A000796, A224719.

%K nonn

%O 1,2

%A _G. L. Honaker, Jr._, Apr 18 2013

%E Additional terms from Mike Keith (mikek314(at)gmail.com), Apr 18 2013