A167504 Number of primes of the form 2^(n-m) 3^m - 1, 0 <= m <= n.

1, 2, 3, 2, 4, 0, 5, 3, 4, 0, 3, 1, 7, 0, 2, 2, 6, 0, 3, 3, 2, 0, 5, 1, 3, 0, 3, 3, 3, 0, 9, 3, 3, 0, 4, 3, 3, 0, 3, 4, 6, 0, 6, 2, 1, 0, 7, 1, 5, 0, 6, 2, 3, 0, 3, 3, 3, 0, 6, 1, 6, 0, 5, 4, 5, 0, 2, 4, 5, 0, 6, 2, 7, 0, 3, 1, 8, 0, 5, 2, 6, 0, 5, 0, 6, 0, 2, 5, 6, 0, 5, 4, 1, 0, 5, 1, 4, 0, 4, 0, 6, 0, 3, 4, 3

Offset: 1

Author

M. F. Hasler, Nov 19 2009

Keywords

• nonn

Links

• M. Underwood, 2^a*3^b one away from a prime. Post to primenumbers group, Nov. 19, 2009.
• Mark Underwood, Jens Kruse Andersen, 2^a*3^b one away from a prime, digest of 3 messages in primenumbers Yahoo group, Nov 19, 2009.

Programs

PARI

A167504(n)=sum(b=0,n,ispseudoprime(3^b<<(n-b)-1))