A142191 Primes congruent to 21 mod 40.

61, 101, 181, 421, 461, 541, 661, 701, 821, 941, 1021, 1061, 1181, 1301, 1381, 1621, 1741, 1861, 1901, 2141, 2221, 2341, 2381, 2621, 2741, 2861, 3061, 3181, 3221, 3301, 3461, 3541, 3581, 3701, 3821, 4021, 4261, 4421, 4621, 4861, 5021, 5101, 5261, 5381, 5501

Offset

1,1

Links

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

Formula

a(n) ~ 16n log n. - Charles R Greathouse IV, Jul 03 2016

Mathematica

Select[Prime[Range[2000]], MemberQ[{21}, Mod[#, 40]]&] (* Vincenzo Librandi, Aug 22 2012 *)
Select[Range[21, 5600, 40], PrimeQ] (* Harvey P. Dale, Oct 04 2015 *)

Prog

(Magma) [p: p in PrimesUpTo(6000) | p mod 40 eq 21 ]; // Vincenzo Librandi, Aug 22 2012
(PARI) is(n)=isprime(n) && n%40==21 \\ Charles R Greathouse IV, Jul 03 2016

Crossrefs

Cf. A000040.

Sequence in context: A142108 A033239 A106390 * A086126 A023287 A203263

Adjacent sequences: A142188 A142189 A142190 * A142192 A142193 A142194

Keyword

nonn,easy

Author

N. J. A. Sloane, Jul 11 2008

Status

approved