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 A228523 #33 Sep 03 2013 17:10:53 %S A228523 7,11,12,14,17,18,19,20,22,23,27,28,29,30,31,32,33,35,36,37,38,41,43, %T A228523 44,45,46,47,48,49,50,51,52,53,54,56,57,58,59,60,61,62,66,67,69,70,71, %U A228523 72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,90,91,92 %N A228523 Numbers that are not the product of two Fibonacci numbers (not necessarily distinct). %C A228523 All primes except prime Fibonacci numbers are in this sequence. %e A228523 Although 12 can be expressed as a product of Fibonacci numbers, it takes three of them, not two, hence 12 is in the list. %e A228523 There is no way to express 14 as a product of Fibonacci numbers since its larger prime factor, 7, is not a Fibonacci number, hence 14 is in the list. %e A228523 16 is not in the list because it can be expressed as 2 * 8. %t A228523 nn = 12; f = Fibonacci[Range[2, nn]]; f2 = Select[Union[Flatten[Outer[Times, f, f]]], # <= f[[-1]] &]; Complement[Range[f[[-1]]], f2] (* _T. D. Noe_, Sep 03 2013 *) %Y A228523 Cf. A049997 (complement). %K A228523 nonn,easy %O A228523 1,1 %A A228523 _Alonso del Arte_, Sep 02 2013