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A098917 Least k such that k*Mersenne-prime(n)*Mersenne-prime(n+1) + 1 is prime. 0
2, 6, 4, 16, 36, 6, 42, 24, 172, 18, 52, 54, 6, 130 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..14.

EXAMPLE

2*(2^2-1)*(2^3-1) + 1 = 43 prime so k(1)=2

2*(2^3-1)*(2^5-1) + 1 = 435 composite

4*(2^3-1)*(2^5-1) + 1 = 867 composite

6*(2^3-1)*(2^5-1) + 1 = 1303 prime so k(2)=6

CROSSREFS

Sequence in context: A226718 A181159 A127320 * A054786 A269372 A282902

Adjacent sequences:  A098914 A098915 A098916 * A098918 A098919 A098920

KEYWORD

nonn

AUTHOR

Pierre CAMI, Oct 17 2004

STATUS

approved

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Last modified December 6 04:14 EST 2019. Contains 329784 sequences. (Running on oeis4.)