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 A147997 #18 Sep 23 2016 12:22:15
%S A147997 1,1,1,2,2,3,5,7,11,18,28,45,73,117,189,306,494,799,1293,2091,3383,
%T A147997 5474,8856,14329,23185,37513,60697,98210,158906,257115,416021,673135,
%U A147997 1089155,1762290,2851444,4613733,7465177,12078909
%N A147997 Number of nonnegative even integers <= Fibonacci(n).
%F A147997 a(n) = 1+floor( A000045(n)/2) = 1+A004695(n). - _R. J. Mathar_, Jan 30 2010
%F A147997 From _Chai Wah Wu_, Sep 23 2016: (Start)
%F A147997 a(n) = a(n-1) + a(n-2) + a(n-3) - a(n-4) - a(n-5) for n > 4.
%F A147997 G.f.: (1 + x)*(1 - x - x^3)/((1 - x)*(1 - x - x^2)*(1 + x + x^2)). (End)
%t A147997 Table[f=Fibonacci[n]; If[EvenQ[f], f = f/2, f = (f-1)/2]; f+1, {n, 0, 100}] (* _Vladimir Joseph Stephan Orlovsky_, Nov 22 2010 *)
%Y A147997 Cf. A000045
%K A147997 easy,nonn
%O A147997 0,4
%A A147997 _Giovanni Teofilatto_, Nov 19 2008
%E A147997 Definition and offset corrected by _R. J. Mathar_, Jan 30 2010
%E A147997 Definition corrected by _Joel B. Lewis_, Nov 14 2012