[seqfan] Re: A Fibonacci-related sequence inspired by Wall-Sun-Sun primes

Neil Sloane njasloane at gmail.com
Fri Dec 19 20:20:06 CET 2014


Felix, Sure, go ahead and submit it!  Thank you.

Best regards
Neil

Neil J. A. Sloane, President, OEIS Foundation.
11 South Adelaide Avenue, Highland Park, NJ 08904, USA.
Also Visiting Scientist, Math. Dept., Rutgers University, Piscataway, NJ.
Phone: 732 828 6098; home page: http://NeilSloane.com
Email: njasloane at gmail.com


On Fri, Dec 19, 2014 at 2:02 PM, Felix Fröhlich <felix.froe at googlemail.com>
wrote:
>
> Hello sequence fans,
>
> the following sequence is inspired by Wall-Sun-Sun primes (see
> http://en.wikipedia.org/wiki/Wall–Sun–Sun_prime):
>
> a(n) = smallest composite c such that p = prime(n) satisfies F_c-(c/p) == 0
> (mod c), where F_k denotes the k-th Fibonacci number and c/p denotes the
> Kronecker symbol. The sequence begins
>
> 12, 12, 25, 168, 660, 323, 377, 442, 552, 442, 323, 1891, 442, 323, 323,
> 323, 377, 323, 377, 323, 323, ....
>
> I used the following PARI program to compute the terms:
>
> forprime(p=1, 1000, c=2; while(Mod(fibonacci(c-kronecker(c, p)), c)!=0 ||
> ispseudoprime(c), c++); print1(c, ", "))
>
> Is this sequence interesting enough to be submitted?
>
> Best regards,
>
> Felix
>
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