OFFSET
1,1
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
MATHEMATICA
Select[Range[1, 5000, 21], PrimeQ] (* Vladimir Joseph Stephan Orlovsky, Apr 03 2011*)
PROG
(Magma) [p: p in PrimesUpTo(5000) | p mod 21 eq 1 ]; // Vincenzo Librandi, Aug 14 2012
(PARI) is(n)=isprime(n) && n%21==1 \\ Charles R Greathouse IV, Jul 01 2016
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
N. J. A. Sloane, Jul 11 2008
STATUS
approved