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

[Felix Fröhlich]

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