A181493 Numbers of the form 3*2^k which are the average of twin primes, i.e., a(n)-1 and a(n)+1 are both prime.

6, 12, 192, 786432

Offset

1,1

Comments

Sequence A181490 lists the exponents k, sequences A181491 and A181492 the corresponding twin primes.

Links

Table of n, a(n) for n=1..4.

Formula

A181493 = A014574 intersect A007283 = A181491 + 1 = A181492 - 1 = 3*2^A181490.

A181493(n) = A007283(A181490(n)).

A181493 = A014574 intersect A007283 = A181491 + 1 = A181492.

A181493(n) = A007283(A181490(n)).

Mathematica

Select[3 2^Range[500], PrimeQ[#-1]&&PrimeQ[#+1]&]  (* Harvey P. Dale, Jan 18 2011 *)

Prog

(PARI) for( k=1, 999, ispseudoprime(3<<k-1)|next; ispseudoprime(3<<k+1)|next; print1(3<<k, ", "))

Crossrefs

Cf. A001097, A001359, A006512, A014574.

Sequence in context: A334805 A324980 A014402 * A360524 A051784 A158046

Adjacent sequences: A181490 A181491 A181492 * A181494 A181495 A181496

Keyword

nonn,bref,more

Author

M. F. Hasler, Oct 30 2010

Status

approved