A242773 - OEIS

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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

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OFFSET

1,1

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

LINKS

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

FORMULA

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

EXAMPLE

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

MATHEMATICA

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

CROSSREFS

Cf. A001359, A174913, A242772.

Sequence in context: A067248 A152007 A350148 * A333338 A131676 A344532

Adjacent sequences: A242770 A242771 A242772 * A242774 A242775 A242776

KEYWORD

nonn

AUTHOR

Ivan N. Ianakiev, May 22 2014

STATUS

approved