OFFSET
1,1
COMMENTS
Other values are a(840)=17 and a(12600)=37. Not all terms are prime; for example, the smallest non-divisor of F(2520) is 25.
It appears that the indices k for which a(n) is not prime are divisible by 2520 and that the sequence k/2520 is A047201. - Michel Marcus, Jul 10 2014
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
MAPLE
f:= proc(n) local m, k;
m:= combinat:-fibonacci(n);
for k from 2 do if m mod k <> 0 then return k fi od:
end proc:
map(f, [$1..100]); # Robert Israel, Mar 06 2020
MATHEMATICA
a[n_] := Module[{f = Fibonacci[n], d}, For[d = 2, True, d++, If[!Divisible[f, d], Return[d]]]];
Array[a, 100] (* Jean-François Alcover, Jul 24 2020 *)
PROG
(PARI) a(n) = my(f = fibonacci(n)); my(d = 2); while((f%d) == 0, d++); d; \\ Michel Marcus, Jul 10 2014
(Sage)
def A152727(n) :
d = 2
f = fibonacci(n)
while ((f % d) == 0) :
d = d + 1
return(d)
[A152727(n) for n in (1..105)] # Jani Melik, Jul 10 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
John W. Layman, Dec 11 2008
STATUS
approved