A180431 - OEIS

%I #11 Feb 21 2023 06:17:26

%S 0,6,522,178438

%N Numbers n such that 4*17^n+1 is prime.

%C For n>0, members of the sequence may only be of form 4k+2 (otherwise the expression is divisible by 3 or 5). Therefore members of the sequence are a subset of A005574 and are Generalized Fermat primes.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/GeneralizedFermatNumber.html">Generalized Fermat Number</a>.

%e For a(2) = 6 we have 4*17^6+1 = 96550277, which is prime.

%t Do[ If[ PrimeQ[ 4*17^n+1], Print[ n ]], {n, 0, 10000}]

%o (PARI) is(n)=isprime(4*17^n+1) \\ _Charles R Greathouse IV_, May 15 2013

%Y Cf. A005574.

%K nonn,more

%O 1,2

%A _Serge Batalov_, Sep 04 2010