A167505 Number of primes of the form 2^(n-m) 3^m + 1, 0 <= m <= n.
1, 2, 2, 2, 3, 2, 3, 4, 4, 3, 2, 0, 5, 1, 1, 6, 6, 2, 5, 1, 1, 2, 5, 0, 3, 1, 2, 2, 4, 2, 5, 3, 0, 1, 6, 2, 8, 2, 2, 3, 9, 1, 7, 4, 4, 0, 6, 0, 3, 3, 2, 7, 8, 1, 4, 4, 1, 2, 6, 0, 5, 2, 4, 2, 2, 1, 11, 4, 3, 1, 3, 0, 6, 0, 2, 3, 4, 1, 6, 0, 4, 3, 8, 2, 2, 2, 2, 1, 3, 1, 2, 3, 3, 1, 3, 0, 5, 1, 2, 1, 7, 0, 7, 2, 2
Offset: 1
Keywords
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
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PARI
A167505(n)=sum(b=0,n,ispseudoprime(3^b<<(n-b)+1))