A242773 The greater of twin primes p2 such that 2*p1 + p2 is a prime number (A174913) and also the lesser of other twin primes in A174913.

7, 11491, 32971, 33331, 33601, 42841, 58111, 93811, 96331, 114601, 180181, 273001, 309541, 334891, 401311, 540541, 633571, 717091, 784351, 820411, 870241, 879691, 907141, 948091, 989251, 991621, 994561, 1020961, 1028581, 1044751, 1185661, 1189651, 1245451, 1253911

Offset: 1

Author

Ivan N. Ianakiev, May 22 2014

Keywords

• nonn

Comments

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

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

Examples

			a(1) = 7, 7 - 2 = 5 = A174913(1) and 2*A174913(1) + 7 = A174913(2).
		

Links

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

Crossrefs

Cf. A001359, A174913, A242772.

Programs

Mathematica

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

Formula

a(n) = A242772(n) + 2.