A199165 Numbers n such that (6^n-11)/5 is prime.
2, 3, 4, 5, 14, 19, 21, 50, 53, 136, 146, 1255, 1448, 1839, 2053, 2496, 4060, 5041, 8410, 14090, 14940, 19759, 29871, 44836, 78175, 114398, 120946, 137845, 461108, 727496, 840316
Offset: 1
Examples
a(4) = 5 because (6^5-11)/5 = 1553 is prime.
Links
- Henri & Renaud Lifchitz, PRP Records.
Programs
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Mathematica
lst={}; Do[If[PrimeQ[(6^n-11)/5], Print[n]; AppendTo[lst, n]], {n, 10^6}]; lst -
PARI
is(n)=ispseudoprime((6^n-11)/5) \\ Charles R Greathouse IV, Jun 13 2017
Extensions
a(23)-a(28) are probable primes discovered by Paul Bourdelais, Nov 15 2011
a(23)-a(28) independently confirmed as probable primes using Mathematica PrimeQ function by Gilbert Mozzo, Nov 21 2011
a(29) corresponds to a probable prime discovered by Paul Bourdelais, Apr 25 2019
a(30) corresponds to a probable prime discovered by Paul Bourdelais, Aug 12 2019
a(31) corresponds to a probable prime discovered by Paul Bourdelais, Jun 18 2020