A181494 Twin primes (A001097) of the form 3*2^k +- 1.

5, 7, 11, 13, 191, 193, 786431, 786433

Offset

1,1

Links

Table of n, a(n) for n=1..8.

Formula

A181494 = A181491 union A181492.

A181494(n) = A181493(ceiling(n/2)) + (-1)^n = A007283(A181490(ceiling(n/2))) + (-1)^n.

Prog

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

Crossrefs

Cf. A001097, A001359, A006512, A014574.

Sequence in context: A220951 A136055 A250127 * A125293 A354164 A098243

Adjacent sequences: A181491 A181492 A181493 * A181495 A181496 A181497

Keyword

more,nonn

Author

M. F. Hasler, Oct 30 2010

Status

approved