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%I #20 Aug 21 2021 13:09:39
%S 4,6,12,16,34,48,68,384,1080,5892,9816
%N Numbers n such that 6^n - 5^n - 4^n - 3^n - 2^n - 1 is prime.
%C a(11) > 7500.
%C All terms are even. - _Jon Perry_, Apr 12 2014
%e 6^4 - 5^4 - 4^4 - 3^4 - 2^4 - 1 = 317 is prime. Thus, 4 is a member of this sequence.
%o (PARI) for(n=1,7500,if(ispseudoprime(6^n-5^n-4^n-3^n-2^n-1),print(n)))
%o (Python)
%o from sympy import isprime
%o def afind(limit, k0=1):
%o pow6, pow5, pow4, pow3, pow2 = 6**k0, 5**k0, 4**k0, 3**k0, 2**k0
%o for k in range(k0, limit+1):
%o if isprime(pow6 - pow5 - pow4 - pow3 - pow2 - 1): print(k, end=", ")
%o pow6 *= 6; pow5 *= 5; pow4 *= 4; pow3 *= 3; pow2 *= 2
%o afind(1100) # _Michael S. Branicky_, Aug 21 2021
%Y Cf. A147977.
%Y Cf. A000043, A240503.
%K nonn,more
%O 1,1
%A _Derek Orr_, Apr 06 2014
%E a(11) from _Michael S. Branicky_, Aug 21 2021
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