A128163 Numbers k such that A128162(k) is prime.

5, 7, 9, 11, 13, 14, 15, 26, 30, 53, 66, 82, 155, 189, 225, 261, 625, 870, 1071, 7655, 8191, 8883, 9226, 12246, 70274, 71595, 108009, 127077

Offset

1,1

Comments

Corresponding primes in A128162 are {3, 3, 31, 37, 137, 347, 487, 77951, 166409, 13506083561, ...}.

Links

Table of n, a(n) for n=1..28.

Mathematica

Do[f=PowerMod[3, n, Fibonacci[n]]; If[PrimeQ[f], Print[{n, f}]], {n, 1, 1071}]
Select[Range[72000], PrimeQ[PowerMod[3, #, Fibonacci[#]]]&] (* Harvey P. Dale, Sep 11 2019 *)

Prog

(PARI) is(n)=ispseudoprime(3^n%fibonacci(n)) \\ Charles R Greathouse IV, Jun 19 2017
(PFGW)
ABC2 3^$a % F($a)
a: from 5 to 1000000
// Charles R Greathouse IV, Jun 19 2017

Crossrefs

Cf. A128162 (3^n modulo Fibonacci(n)), A128161, A057862 (2^n modulo Fibonacci(n)).

Sequence in context: A175382 A279244 A325797 * A177088 A362486 A168146

Adjacent sequences: A128160 A128161 A128162 * A128164 A128165 A128166

Keyword

hard,more,nonn

Author

Alexander Adamchuk, Feb 19 2007

Extensions

Corrected and extended by Stefan Steinerberger, Jun 10 2007

a(25)-a(26) from Donovan Johnson, Sep 03 2008

a(27)-a(28) from Michael S. Branicky, Nov 21 2024

Status

approved