A252090 Primes p such that p + 28 is also prime.

3, 13, 19, 31, 43, 61, 73, 79, 103, 109, 139, 151, 163, 199, 211, 223, 229, 241, 283, 331, 373, 421, 433, 439, 463, 541, 571, 613, 619, 631, 673, 691, 733, 769, 811, 829, 853, 859, 883, 919, 991, 1021, 1033, 1063, 1069, 1123, 1153, 1201, 1231, 1249

Offset

1,1

Links

Karl V. Keller, Jr., Table of n, a(n) for n = 1..10000

Example

19 is in the sequence because 19 is prime and 19 + 28 = 47 is also prime.
433 is in the sequence because 433 is prime and 433 + 28 = 461 is also prime.

Maple

P:= select(isprime, {seq(2*i+1, i=1..10000)}):
P intersect map(`-`, P, 28);
# if using Maple 11 or earlier, uncomment the next line
# sort(convert(%, list));  # Robert Israel, Dec 14 2014

Mathematica

Select[Prime[Range[250]], PrimeQ[# + 28] &]

Prog

(Magma) [NthPrime(n): n in [1..250] | IsPrime(NthPrime(n)+28)];
(PARI) is(n)=isprime(n)&&isprime(n+28) \\ Anders Hellström, Dec 01 2015

Crossrefs

Sequence in context: A045435 A038974 A168425 * A079419 A117300 A023215

Adjacent sequences: A252087 A252088 A252089 * A252091 A252092 A252093

Keyword

nonn,easy

Author

Vincenzo Librandi, Dec 14 2014

Status

approved