This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A280592 #23 Jul 04 2021 10:54:56
%S A280592 1,2,3,4,6,15,16,20,24,30,185,219,273,285,292,296,304,315,364,370,380,
%T A280592 432,438,444,456,468,504,540,546,570,630,3235,5176,6470,7764,46843,
%U A280592 47423,47693,48053,50431,52403,56231,57965,59555,62855,67655,67865,70735,72123,72297,73473
%N A280592 Numbers n such that phi(n) is a Fibonacci number.
%C A280592 Note that the sequence of corresponding Fibonacci numbers is not the same as A134492. See also A280681.
%H A280592 Robert Israel, <a href="/A280592/b280592.txt">Table of n, a(n) for n = 1..2075</a>
%e A280592 24 is a term because phi(24) = 8 is a Fibonacci number.
%p A280592 fibs:= {seq(combinat:-fibonacci(n),n=1..30)}:
%p A280592 N:= combinat:-fibonacci(31):
%p A280592 sort(convert(select(t -> t <= N, map(t -> op(numtheory:-invphi(t)), fibs)), list)); # _Robert Israel_, Nov 20 2019
%t A280592 Module[{fibs=Fibonacci[Range[30]]},Select[Range[80000],MemberQ[ fibs,EulerPhi[ #]]&]] (* _Harvey P. Dale_, Jul 04 2021 *)
%o A280592 (PARI) isFibonacci(n)=my(k=n^2); issquare(k+=(k+1)<<2) || (n>0 && issquare(k-8));
%o A280592 is(n)=isFibonacci(eulerphi(n));
%Y A280592 Cf. A000010, A000045, A134492, A280681.
%K A280592 nonn,look
%O A280592 1,2
%A A280592 _Altug Alkan_, Jan 06 2017