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A098920 Least k such that k*M#(n) +1 is prime with M#(n)=product from 1 to n of Mersenne-primes. 0
2, 2, 2, 6, 30, 10, 4, 26, 12, 10, 12, 436, 644, 424, 2164, 862, 408, 9558, 5226, 12350 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..20.

EXAMPLE

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

CROSSREFS

Sequence in context: A213170 A321741 A101416 * A270557 A129365 A125838

Adjacent sequences:  A098917 A098918 A098919 * A098921 A098922 A098923

KEYWORD

hard,more,nonn

AUTHOR

Pierre CAMI, Oct 17 2004

EXTENSIONS

a(15)-a(20) from Donovan Johnson, Mar 23 2008

STATUS

approved

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Last modified October 21 14:49 EDT 2019. Contains 328301 sequences. (Running on oeis4.)