A167505 - OEIS

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

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..105.

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.

PROG

(PARI) A167505(n)=sum(b=0, n, ispseudoprime(3^b<<(n-b)+1))

CROSSREFS

Cf. A167504, A167506.

Sequence in context: A289437 A348369 A068324 * A360998 A165015 A178994

Adjacent sequences: A167502 A167503 A167504 * A167506 A167507 A167508

KEYWORD

nonn

AUTHOR

M. F. Hasler, Nov 19 2009

STATUS

approved