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A107639 Smallest prime a such that (a*b)^2 + a*b -1 is prime with b prime = 2^(2*n) - 2^n - 1, see A098845 for n. 0

%I

%S 5,7,31,11,5,3,809,661,139,73,521,701,131,487,89,211,733,3011,311,

%T 8837,2837,8831,1733,401,983,17881,1783,19553,13859

%N Smallest prime a such that (a*b)^2 + a*b -1 is prime with b prime = 2^(2*n) - 2^n - 1, see A098845 for n.

%e 2^4-2^2-1=3=b(1) prime, (3*3)^2+3*3-1=89 prime so a(1)=3

%e 2^8-2^4-1=239=b(2) prime, (7*239)^2+7*239-1=2800601 prime so a(2)=7

%Y Cf. A098845.

%K hard,more,nonn

%O 1,1

%A _Pierre CAMI_, Jun 10 2005

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Last modified September 22 16:33 EDT 2020. Contains 337291 sequences. (Running on oeis4.)