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 A075731 #4 Mar 31 2012 14:39:59 %S A075731 1,1,2,5,8,13,55,89,233,377,610,1597,4181,10946,17711,28657,121393, %T A075731 514229,832040,1346269,3524578,5702887,9227465,24157817,39088169, %U A075731 63245986,165580141,267914296,433494437,1836311903,2971215073 %N A075731 Fibonacci numbers F(k) for k squarefree (A005117). %e A075731 10 is squarefree and fibonacci(10)=55, 11 is squarefree and fibonacci(11)=89. %p A075731 with(combinat, fibonacci): fib_dsk := proc(n); if (numtheory[issqrfree](n)='true') then RETURN(fibonacci(n)); fi; end: seq(fib_dsk(i), i=1..100); %Y A075731 Cf. A000045, A005117, A061305. %K A075731 easy,nonn %O A075731 1,3 %A A075731 _Jani Melik_, Oct 07 2002