A272366 Numbers n such that 5^n-4^(n+1) is prime.

7, 25, 29, 55, 75, 243, 345, 635, 899, 2025, 2105, 2295, 5057, 5155, 5209, 11115, 81743, 97615

Offset

1,1

Comments

a(19) > 10^5.

Links

Table of n, a(n) for n=1..18.

Example

7 is a member since 5^7 - 4^8 = 78125 - 65536 = 12589 which is a prime number.

Mathematica

Select[Range[0, 100000], PrimeQ[5^# - 4^(# + 1)] &]

Prog

(PARI) is(n)=ispseudoprime(5^n-4^(n+1)) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Cf. A093713, A082103, A093717, A093793, A096185, A093794, A093795, A096186, A271883, A271884.

Sequence in context: A178370 A034125 A196013 * A327107 A075926 A368532

Adjacent sequences: A272363 A272364 A272365 * A272367 A272368 A272369

Keyword

nonn,more

Author

Robert Price, Apr 27 2016

Status

approved