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%I #8 Apr 03 2023 10:36:12
%S 3,5,4,3,12,44,37,7,2,7,27,80,14,32,12,14,53,32,3,87,62,13,32,13,237,
%T 147,35,63,48,35,32,44,34,32,18,28,17,12,130,250,47,108,112,73,25,5,
%U 149,44,14,129,208,238,10,13,212,124,37,180,80,212,4,19,124,42,17,112,47,27,214,84,95,182,73,957,59,68,47,13,199,130,194,75,24
%N Least k such that k*666^n-1 is prime.
%H C. Caldwell and P. Kaiser, <a href="https://t5k.org/primes/page.php?id=101882">139·666^178851 - 1</a>, Sep 08 2011
%e a(1)=3 since 3*666 is the least multiple of 666^1 such that k*666^1-1 is prime.
%e a(178851) <= 139 since 139*666^178851-1 is prime (cf. link).
%o (PARI) a(n)={ n=666^n; for(k=1,1e9,ispseudoprime(k*n-1)&return(k)) }
%o for(e=1,199,for(k=1,1e9,ispseudoprime(k*666^e-1)&!print1(k",")&break))
%Y Cf. A037029, A037030, A063472, A195131.
%K nonn
%O 1,1
%A _M. F. Hasler_, Sep 09 2011