A141890 Primes congruent to 5 mod 21.

5, 47, 89, 131, 173, 257, 383, 467, 509, 593, 677, 719, 761, 887, 929, 971, 1013, 1097, 1181, 1223, 1307, 1433, 1559, 1601, 1811, 1979, 2063, 2273, 2357, 2399, 2441, 2609, 2693, 2777, 2819, 2861, 2903, 3323, 3407, 3449, 3491, 3533, 3617, 3659, 3701, 3911

Offset: 1

Author

N. J. A. Sloane, Jul 11 2008

Keywords

• nonn
• easy

Links

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

Crossrefs

Cf. A000040, A124826.

Programs

Magma

[p: p in PrimesUpTo(6000) | p mod 21 eq 5 ]; // Vincenzo Librandi, Aug 16 2012

Mathematica

Select[Range[5,5000,21],PrimeQ] (* Vladimir Joseph Stephan Orlovsky, Apr 03 2011*)
Select[Prime[Range[600]],Mod[#,21]==5&] (* Harvey P. Dale, Jan 30 2021 *)

PARI

is(n)=isprime(n) && n%21==5 \\ Charles R Greathouse IV, Jul 03 2016

Formula

a(n) ~ 12n log n. - Charles R Greathouse IV, Jul 03 2016