A142192 Primes congruent to 23 mod 40.

23, 103, 223, 263, 383, 463, 503, 743, 823, 863, 983, 1063, 1103, 1223, 1303, 1423, 1543, 1583, 1663, 1783, 1823, 2063, 2143, 2383, 2423, 2503, 2543, 2663, 2903, 3023, 3343, 3463, 3583, 3623, 3823, 3863, 3943, 4423, 4463, 4583, 4663, 4703, 4783, 4903, 4943

Offset

1,1

Comments

Also primes of the form 2*x^2 + 5*y^2 (see Uspensky and Heaslet). - Stefano Spezia, Jun 28 2026

References

J. V. Uspensky and M. A. Heaslet, Elementary Number Theory, McGraw-Hill, NY, 1939, Exercise n. 2 at p. 346.

Links

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

Formula

a(n) ~ 16n log n. - Charles R Greathouse IV, Jul 02 2016

Mathematica

Select[Prime[Range[2000]], MemberQ[{23}, Mod[#, 40]]&] (* Vincenzo Librandi, Aug 22 2012 *)
(* Alternative: *)
Select[Range[23, 5000, 40], PrimeQ] (* Harvey P. Dale, Apr 22 2018 *)

Prog

(Magma) [p: p in PrimesUpTo(6000) | p mod 40 eq 23 ]; // Vincenzo Librandi, Aug 22 2012
(PARI) is(n)=isprime(n) && n%40==23 \\ Charles R Greathouse IV, Jul 02 2016

Crossrefs

Cf. A000040.

Sequence in context: A214092 A139976 A241746 * A129918 A240839 A138715

Adjacent sequences: A142189 A142190 A142191 * A142193 A142194 A142195

Keyword

nonn,easy,changed

Author

N. J. A. Sloane, Jul 11 2008

Status

approved