A075739 Nonsquarefree Fibonacci numbers whose indices are also not squarefree.
144, 2584, 46368, 75025, 14930352, 4807526976, 12586269025, 86267571272, 225851433717, 1548008755920, 498454011879264, 2111485077978050, 160500643816367088, 2880067194370816120, 51680708854858323072, 354224848179261915075, 16641027750620563662096
Offset: 1
Examples
Fib(18)=2584 is there because neither 18 nor 2584 is squarefree.
Programs
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Maple
with(combinat, fibonacci): fib_supM_ndsk := proc(n); if (numtheory[issqrfree](n)='false') then if (numtheory[issqrfree](fibonacci(n))='false') then RETURN(fibonacci(n)); fi; fi; end: seq(fib_supM_ndsk(i), i=1..200);
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Mathematica
Select[Table[{n,Fibonacci[n]},{n,300}],NoneTrue[#,SquareFreeQ]&][[All,2]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Aug 20 2019 *)
Extensions
Edited by Don Reble, Nov 05 2005
More terms from Harvey P. Dale, Aug 20 2019