A057909
Numbers k such that 4^k + k is prime.
Original entry on oeis.org
1, 3, 9, 15, 37, 85, 133, 225, 1233, 12793, 108889
Offset: 1
-
Do[ If[ PrimeQ[ 4^n + n ], Print[ n ] ], {n, 0, 3000} ]
-
is(n)=ispseudoprime(4^n+n) \\ Charles R Greathouse IV, Jun 13 2017
A121823
(3^p+p)/(p+1) with (p + 1) odd prime > 3.
Original entry on oeis.org
17, 105, 5369, 40881, 2532161, 20390553, 1364393897, 788854912241, 6641649422409, 4056611764783761, 296528425830656801, 2544627654221217657, 188573151481968108425, 121907205457107043376081, 79832689783834658219010233, 694937020905183664168761201, 461241110188546453162994653785, 35255711337932980300219323747689
Offset: 1
a(1) = (3^4 + 4)/(4+1) = 17, a(2) = (3^6 + 6)/(6+1) = 105.
-
map(t -> (3^(t-1)+t-1)/t, select(isprime,[seq(i,i=5..100,2)])); # Robert Israel, Nov 13 2017
Corrected and edited according to suggestion of Michel Marcus by
Zak Seidov, Oct 20 2013
A273942
Primes of the form 3^k + k.
Original entry on oeis.org
11, 6569, 16677181699666603
Offset: 1
-
[a: n in [0..100] | IsPrime(a) where a is 3^n+n];
-
Select[Table[3^n + n, {n, 1, 1000}], PrimeQ]
A382786
Numbers k such that 5^k + k is prime.
Original entry on oeis.org
7954, 22102, 33054, 135156
Offset: 1
Showing 1-4 of 4 results.
Comments