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A146524 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. 1
3, 1, 3, 0, 1, 1, 0, 1, 2, 0, 1, 0, 0, 1, 2, 0, 0, 3, 0, 1, 1, 0, 1, 0, 0, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 2, 0, 1, 0, 0, 1, 0, 0, 0, 2, 0, 1, 1, 0, 1, 1, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 1, 2, 0, 0, 0, 0, 1, 1, 0, 0, 2, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 0, 1, 1, 0, 1, 2, 0, 0, 0, 0, 0, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

EXAMPLE

For n = 3: 2*3*1 +1 = 7, which is prime. 2*3*2 + 1 = 13, which is prime. 2*3*3 + 1 = 19, which is prime. But 2*3*4 + 1 = 25, which is composite. So a(3) = 3, because there are 3 primes in the arithmetic sequence before hitting a composite.

CROSSREFS

A146525

Sequence in context: A143783 A179175 A274635 * A179656 A167274 A201679

Adjacent sequences:  A146521 A146522 A146523 * A146525 A146526 A146527

KEYWORD

nonn

AUTHOR

Leroy Quet, Oct 30 2008

EXTENSIONS

Extended by Ray Chandler, Nov 01 2008

STATUS

approved

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Last modified January 16 18:17 EST 2022. Contains 350376 sequences. (Running on oeis4.)