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%I #24 Sep 08 2022 08:45:35
%S 41,83,167,251,293,419,461,503,587,797,839,881,1049,1091,1217,1259,
%T 1301,1427,1511,1553,1637,1721,1847,1889,1931,1973,2099,2141,2267,
%U 2309,2351,2393,2477,2687,2729,2897,2939,3023,3191,3359,3527,3779,3821,3863,3947
%N Primes congruent to 20 mod 21.
%H Vincenzo Librandi, <a href="/A141898/b141898.txt">Table of n, a(n) for n = 1..1000</a>
%F a(n) ~ 12n log n. - _Charles R Greathouse IV_, Jul 02 2016
%t Select[Range[20,5000,21],PrimeQ] (* _Vladimir Joseph Stephan Orlovsky_, Apr 04 2011*)
%o (Magma) [ p: p in PrimesUpTo(5000) | p mod 21 eq 20 ]; // _Vincenzo Librandi_, Apr 05 2011
%o (PARI) is(n)=isprime(n) && n%21==20 \\ _Charles R Greathouse IV_, Jul 02 2016
%o (GAP) A141898:=Filtered(Filtered([1..10^3],IsPrime),i-> i mod 21 = 20); # _Muniru A Asiru_, Oct 09 2017
%Y Cf. A000040, A124826.
%K nonn,easy
%O 1,1
%A _N. J. A. Sloane_, Jul 11 2008