A242772 The lesser of twin primes p1 such that 2*p1 + p2 is a prime number (A174913) and also the lesser of other twin primes in A174913.

5, 11489, 32969, 33329, 33599, 42839, 58109, 93809, 96329, 114599, 180179, 272999, 309539, 334889, 401309, 540539, 633569, 717089, 784349, 820409, 870239, 879689, 907139, 948089, 989249, 991619, 994559, 1020959, 1028579, 1044749, 1185659, 1189649, 1245449, 1253909

Offset

1,1

Comments

It seems that a(n) == 9 mod 10 for n > 1.

a(n) == 9 (mod 10) for n > 1 since if p1 == 1, 3 or 7 (mod 10) then 2*p1 + p2, p2, or 2*p1 + p2 + 2 is divisible by 5, respectively. - Amiram Eldar, Dec 31 2019

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Example

a(1) = A174913(2) = 5 and 2*5 + 7 = 17 = A174913(3).

Mathematica

Select[Range[10^6], And @@ PrimeQ[{#, # + 2, (p = 3*# + 2), p + 2, 3*p + 2}] &] (* Amiram Eldar, Dec 31 2019 *)

Prog

(PARI) isok(p) = isprime(p) && isprime(p+2) && isprime(q=3*p+2) && isprime(q+2) && isprime(3*q+2); \\ Michel Marcus, May 23 2014

Crossrefs

Cf. A001359, A174913, A174920, A242773.

Sequence in context: A292742 A260262 A058051 * A368067 A364691 A367943

Adjacent sequences: A242769 A242770 A242771 * A242773 A242774 A242775

Keyword

nonn

Author

Ivan N. Ianakiev, May 22 2014

Status

approved