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%I #16 Nov 24 2024 04:02:36
%S 1,3,7,98,104,128,180,834,1633,8000,28538,46605,131941,147684,433734
%N Numbers k such that k * 14^k - 1 is prime.
%C a(16) > 500000.
%H Steven Harvey, <a href="http://harvey563.tripod.com/GeneralizedWoodallPrimes.txt">Generalized Woodall Search</a>
%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Woodall_number">Woodall number</a>
%t Select[Range[1, 10000], PrimeQ[n*14^n-1] &]
%o (PARI) for(n=1, 10000, if(isprime(n*14^n-1), print1(n", ")))
%o (Magma) [n: n in [1..10000] |IsPrime(n*14^n-1)];
%Y Numbers n such that n * b^n - 1 is prime: A008864 (b=1), A002234 (b=2), A006553 (b=3), A086661 (b=4), A059676 (b=5), A059675 (b=6), A242200 (b=7), A242201 (b=8), A242202 (b=9), A059671 (b=10), A299374 (b=11), A299375 (b=12), A299376 (b=13), this sequence (b=14), A299378 (b=15), A299379 (b=16), A299380 (b=17), A299381 (b=18), A299382 (b=19), A299383 (b=20).
%K nonn,more,hard,changed
%O 1,2
%A _Tim Johannes Ohrtmann_, Feb 08 2018