A146525 - OEIS

A146525

a(n) is the largest nonnegative integer m such that 2*n*k-1 is prime for all k where 1<=k<=m. a(n) = 0 if 2n-1 is composite.

0, 3, 5, 1, 0, 2, 1, 0, 1, 1, 0, 3, 0, 0, 3, 1, 0, 0, 1, 0, 2, 1, 0, 1, 0, 0, 2, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0, 3, 0, 0, 5, 0, 0, 0, 1, 0, 1, 1, 0, 1, 1, 0, 2, 0, 0, 0, 0, 0, 0, 1, 0, 2, 0, 0, 1, 1, 0, 0, 0, 0, 1, 1, 0, 0, 1, 0, 0, 1, 0, 1, 0, 0, 3, 0, 0, 2, 1, 0, 0, 0, 0, 2, 1, 0, 1, 1, 0, 0, 0, 0, 0

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OFFSET

1,2

LINKS

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

EXAMPLE

For n = 3: 2*3*1 -1 = 5, which is prime. 2*3*2 - 1 = 11, which is prime. 2*3*3 - 1 = 17, which is prime. 2*3*4 -1 = 23, which is prime. 2*3*5 -1 = 29, which is prime. But 2*3*6 - 1 = 35, which is composite. So a(3) = 5, because there are 5 primes in the arithmetic sequence before hitting a composite.

CROSSREFS

A146524

Sequence in context: A113039 A093016 A031018 * A196611 A011353 A016452

Adjacent sequences: A146522 A146523 A146524 * A146526 A146527 A146528

KEYWORD

nonn

AUTHOR

Leroy Quet, Oct 30 2008

EXTENSIONS

Extended by Ray Chandler, Nov 01 2008

STATUS

approved