A067559 - OEIS

A067559

Numbers n such that floor(Pi*n^2) is prime.

1, 6, 17, 31, 34, 41, 45, 50, 51, 61, 69, 73, 74, 81, 103, 108, 111, 142, 148, 175, 192, 201, 202, 203, 232, 234, 273, 277, 281, 310, 319, 329, 342, 348, 349, 351, 378, 387, 416, 421, 428, 435, 459, 478, 486, 521, 526, 575, 593, 597, 603, 605, 623, 648, 661

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

EXAMPLE

Floor[Pi*6^2] = 113, a prime, so 6 is a term of the sequence.

MATHEMATICA

Select[Range[1, 10^3], PrimeQ[Floor[Pi * #^2]] &]

PROG

(PARI) is(n)=isprime(floor(Pi*n^2)) \\ Charles R Greathouse IV, May 22 2017

CROSSREFS