%I #9 Oct 03 2015 23:21:21
%S 8,21,34,55,144,377,2584,4181,6765,17711,46368,75025,121393,196418,
%T 317811,832040,1346269,2178309,5702887,14930352,102334155,165580141,
%U 267914296,701408733,1134903170,4807526976,12586269025,32951280099
%N Fibonacci numbers with a non-Fibonacci number of divisors.
%C A000005(a(n)) is a non-Fibonacci number A001690.
%e 34 belongs to the sequence because the number of its divisors, 4, is not a Fibonacci number.
%p A000045 := proc(n) option remember ; coeftayl( x/(1-x-x^2),x=0,n) ; end: isA000045 := proc(n) local a; for a from 0 do if A000045(a) > n then RETURN(false) ; elif A000045(a)=n then RETURN(true) ; fi ; od: end: A000005 := proc(n) numtheory[tau](n) ; end: isA139590 := proc(n) RETURN(isA000045(n) and not isA000045(A000005(n))) ; end: for i from 1 to 130 do a000045 := A000045(i) ; if isA139590(a000045) then printf("%d,",a000045) ; fi ; od: # _R. J. Mathar_, May 11 2008
%p with(combinat): with(numtheory): F:={seq(fibonacci(j),j=1..30)}: a:= proc(n) if member(tau(fibonacci(n)),F) = false then fibonacci(n) else end if end proc: seq(a(n),n=1..50); # _Emeric Deutsch_
%t With[{fibs=Fibonacci[Range[60]]},Transpose[Select[Thread[{fibs, DivisorSigma[ 0,fibs]}], !MemberQ[ fibs,#[[2]]]&]][[1]]] (* _Harvey P. Dale_, Aug 04 2013 *)
%Y Cf. A000005, A000045, A001690, A063375, A133021.
%K nonn
%O 1,1
%A _Omar E. Pol_, May 09 2008
%E More terms from _R. J. Mathar_ and _Emeric Deutsch_, May 11 2008