A247091 Least k such that k*n+1 is a prime divisor of Fibonacci(k).

10, 14, 46, 15, 42, 90, 324, 11, 22, 28, 78, 55, 70, 162, 148, 130, 164, 120, 160, 21, 120, 864, 936, 125, 396, 230, 80, 81, 912, 74, 1008, 615, 530, 82, 102, 703, 834, 80, 172, 75, 228, 60, 306, 432, 238, 468, 1830, 181, 1302, 198, 868, 454, 4350, 40, 508

Offset

1,1

Links

Michel Lagneau, Table of n, a(n) for n = 1..500

Formula

a(n) = (A168171(n) - 1)/n. - Michel Marcus, Nov 29 2014

Example

a(3)=46 because Fibonacci(46) = 139*461*28657 and 46*3+1 = 139 is a prime divisor of Fibonacci(46).

Mathematica

lst={}; Do[k=1; While[!PrimeQ[k*n+1]||Mod[Fibonacci[k], k*n+1]>0, k++]; AppendTo[lst, k], {n, 1, 60}]; lst

Prog

(PARI) a(n) = {k = 1; while (! ((isprime(p=k*n+1) && ((fibonacci(k) % p) == 0))), k++); k; } \\ Michel Marcus, Nov 18 2014

Crossrefs

Cf. A000045, A168171.

Sequence in context: A328635 A260564 A107126 * A025122 A173684 A258287

Adjacent sequences: A247088 A247089 A247090 * A247092 A247093 A247094

Keyword

nonn

Author

Michel Lagneau, Nov 18 2014

Extensions

Missing term a(419) in b-file inserted by Andrew Howroyd, Feb 23 2018

Status

approved