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

Author

M. F. Hasler, Oct 30 2010

Keywords

• nonn
• bref
• more

Comments

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

Crossrefs

Cf. A001097, A001359, A006512, A014574.

Programs

Mathematica

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

PARI

for( k=1,999, ispseudoprime(3<
				

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)).