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A270102 Numbers k such that 3^k - k*2^k is prime.

%I A270102 #35 May 19 2025 11:09:02
%S A270102 3,4,5,7,8,10,11,23,34,62,95,128,173,251,260,464,628,1267,1895,2057,
%T A270102 2743,5102,7790,49163
%N A270102 Numbers k such that 3^k - k*2^k is prime.
%C A270102 a(25) > 10^5. - _Michael S. Branicky_, Oct 13 2024
%e A270102 n = 4 is a term since 3^4 - 4*2^4 = 17 is prime.
%p A270102 A270102:=n->`if`(isprime(3^n-n*2^n),n,NULL): seq(A270102(n),n=1..2000); # _Wesley Ivan Hurt_, May 08 2016
%t A270102 Select[Range[1, 1000], PrimeQ[3^# - #*2^#] &] (* _Vaclav Kotesovec_, Mar 11 2016 *)
%o A270102 (MATLAB)
%o A270102 if isprime(3^n - n*2^n)
%o A270102 disp(n)
%o A270102 end
%o A270102 (Python)
%o A270102 from gmpy2 import is_prime
%o A270102 for n in range(5000):
%o A270102    if(is_prime(3**n-n*2**n)):print(n,end=", ")
%o A270102 # _Soumil Mandal_, May 08 2016
%o A270102 (PARI) is(n)=ispseudoprime(3^n-n*2^n) \\ _Charles R Greathouse IV_, Jun 06 2017
%Y A270102 Cf. A057468, A270104.
%K A270102 nonn,more
%O A270102 1,1
%A A270102 _Vardan Semerjyan_, Mar 11 2016
%E A270102 a(24) from _Giovanni Resta_, May 05 2016