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

3, 4, 5, 7, 8, 10, 11, 23, 34, 62, 95, 128, 173, 251, 260, 464, 628, 1267, 1895, 2057, 2743, 5102, 7790, 49163

Offset

1,1

Links

Table of n, a(n) for n=1..24.

Example

n = 4 is a term since 3^4 - 4*2^4 = 17 is prime.

Maple

A270102:=n->`if`(isprime(3^n-n*2^n), n, NULL): seq(A270102(n), n=1..2000); # Wesley Ivan Hurt, May 08 2016

Mathematica

Select[Range[1, 1000], PrimeQ[3^# - #*2^#] &] (* Vaclav Kotesovec, Mar 11 2016 *)

Prog

(MATLAB)
if isprime(3^n - n*2^n)
disp(n)
end
(Python)
from gmpy2 import is_prime
for n in range(5000):
   if(is_prime(3**n-n*2**n)):print(n, end=", ")
# Soumil Mandal, May 08 2016
(PARI) is(n)=ispseudoprime(3^n-n*2^n) \\ Charles R Greathouse IV, Jun 06 2017

Crossrefs

Cf. A057468, A270104.

Sequence in context: A287127 A174681 A267650 * A026347 A187482 A285950

Adjacent sequences: A270099 A270100 A270101 * A270103 A270104 A270105

Keyword

nonn,more

Author

Vardan Semerjyan, Mar 11 2016

Extensions

a(24) from Giovanni Resta, May 05 2016

Status

approved