A128945 Numbers n such that the greatest prime < 2^n is a twin prime member.

2, 3, 4, 5, 6, 10, 12, 16, 20, 149, 150, 476, 594, 788, 1574, 1664, 1691, 6117, 6242

Offset

1,1

Comments

A014234(a(n)) is in A001097 (twin primes).

Links

Table of n, a(n) for n=1..19.

Example

For n=5, 31 is the greatest prime < 2^5 and is a member of the twin prime pair 29, 31.

Prog

(PARI) g(n, b)=for(x=1, n, y=precprime(b^x); if(ispseudoprime(y-2), print1(x", ")))

Crossrefs

Sequence in context: A353385 A018266 A344826 * A318533 A048569 A033085

Adjacent sequences: A128942 A128943 A128944 * A128946 A128947 A128948

Keyword

hard,more,nonn

Author

Cino Hilliard, Apr 28 2007

Extensions

Edited by and terms a(15)-a(17) from Ray Chandler, May 12 2007

a(18), a(19) Donovan Johnson, Feb 21 2008

Status

approved