A066774 A066728(a(n))=3.

4, 13, 15, 19, 21, 27, 31, 35, 37, 39, 51, 53, 57, 65, 67, 69, 77, 83, 87, 89, 95, 109, 111, 113, 125, 127, 129, 131, 139, 155, 157, 161, 177, 181, 199, 209, 211, 221, 233, 237, 249, 251, 257, 263, 267, 291, 293, 305, 307, 309, 317, 329, 335, 337, 353, 365, 371

Offset

1,1

Comments

Conjecture: the set of k such that a(k+1)-a(k)=2 is infinite.

Links

Table of n, a(n) for n=1..57.

Formula

If a(k+1)-a(k)=2 then a(k) or a(k+1) is prime. For example : a(9)-a(8)=37-35 and a(9)=37 is prime. a(16)-a(15)=69-67=2 and a(15)=67 is prime.

Crossrefs

Cf. A066728.

Sequence in context: A135406 A066825 A014563 * A075339 A089733 A126908

Adjacent sequences: A066771 A066772 A066773 * A066775 A066776 A066777

Keyword

nonn

Author

Benoit Cloitre, Jan 16 2002

Status

approved