A265486 Numbers k such that 64^k - 8^k - 1 is prime.

3, 6, 15, 19, 36, 75, 80, 118, 199, 336, 360, 520, 1282, 1810, 2872, 4870, 14467, 15102, 22499, 24675, 45615, 105648, 116432

Offset: 1

Author

Vincenzo Librandi, Dec 12 2015

Keywords

• nonn
• more

Comments

For k = 3, 6, 15, 19 the corresponding primes are 261631, 68719214591, 1237940039285345090527035391, 20769187434139310370006797241024511.

3*a(n) belongs to A098845 (the terms from a(18) to a(23) are derived from that sequence).

Examples

			3 is in the sequence because 64^3 - 8^3 - 1 = 261631 is prime.
		

Crossrefs

Cf. A098845, similar sequences listed in A265481.

Programs

Magma

[n: n in [0..300] | IsPrime(64^n-8^n-1)];

Mathematica

Select[Range[1000], PrimeQ[64^# - 8^# - 1] &]

PARI

for(n=1, 1e3, if(ispseudoprime(64^n - 8^n - 1), print1(n, ", "))) \\ Altug Alkan, Dec 12 2015