OFFSET
1,2
COMMENTS
LINKS
Robert Israel, Table of n, a(n) for n = 1..2075
EXAMPLE
24 is a term because phi(24) = 8 is a Fibonacci number.
MAPLE
fibs:= {seq(combinat:-fibonacci(n), n=1..30)}:
N:= combinat:-fibonacci(31):
sort(convert(select(t -> t <= N, map(t -> op(numtheory:-invphi(t)), fibs)), list)); # Robert Israel, Nov 20 2019
MATHEMATICA
Module[{fibs=Fibonacci[Range[30]]}, Select[Range[80000], MemberQ[ fibs, EulerPhi[ #]]&]] (* Harvey P. Dale, Jul 04 2021 *)
PROG
(PARI) isFibonacci(n)=my(k=n^2); issquare(k+=(k+1)<<2) || (n>0 && issquare(k-8));
is(n)=isFibonacci(eulerphi(n));
CROSSREFS
KEYWORD
nonn,look
AUTHOR
Altug Alkan, Jan 06 2017
STATUS
approved