OFFSET
0,3
COMMENTS
LINKS
Robert Israel, Table of n, a(n) for n = 0..2000
EXAMPLE
MAPLE
F:= combinat:-fibonacci:
L:= n -> 2*F(n+1)-F(n):
f:= proc(n) local a, b, k;
if n mod 3 = 0 then return -1 fi;
a:= F(n); b:= L(n);
for k from 2 by 2 do
if isprime(a+k*b) then return k fi
od
end proc:
f(0):= 1: f(1):= 1:
map(f, [$0..100]);
MATHEMATICA
a={}; nmax=79; For[n=0, n<=nmax, n++, If[n>0 && Divisible[n, 3], AppendTo[a, -1], For[k=1, k>0, k++, If[PrimeQ[Fibonacci[n]+k LucasL[n]], AppendTo[a, k]; k=-1]]]]; a(* Stefano Spezia, Sep 15 2022 *)
PROG
CROSSREFS
KEYWORD
sign
AUTHOR
J. M. Bergot and Robert Israel, Sep 13 2022
STATUS
approved