A348421 Primes p == 3 (mod 4) such that (p+3)/2 is not prime.

47, 67, 107, 127, 151, 167, 179, 227, 239, 263, 283, 307, 347, 367, 431, 439, 467, 487, 491, 503, 547, 571, 587, 599, 607, 643, 647, 683, 719, 727, 739, 751, 787, 811, 823, 827, 887, 907, 947, 967, 983, 991, 1019, 1031, 1051, 1063, 1087, 1103, 1163, 1187

Offset

1,1

Comments

Complement of A092109 with respect to A002145.

Links

Jianing Song, Table of n, a(n) for n = 1..10000

Formula

a(n) = 2*A348423(n) - 3.

Example

47 is a term since it is a prime congruent to 3 modulo 4 and (47+3)/2 = 25 is composite.

Mathematica

Select[4*Range[0, 300] + 3, PrimeQ[#] && ! PrimeQ[(# + 3)/2] &] (* Amiram Eldar, Oct 18 2021 *)

Prog

(PARI) isA348421(n) = isprime(n) && (n%4==3) && !isprime((n+3)/2)

Crossrefs

Cf. A002145, A092109, A348423.

Sequence in context: A163390 A332078 A023303 * A106874 A245745 A023331

Adjacent sequences: A348418 A348419 A348420 * A348422 A348423 A348424

Keyword

nonn,easy

Author

Jianing Song, Oct 18 2021

Status

approved