%I A065494
%S A065494 1,2,4,8,15,30,57,112,216,420,815,1580,3069,5950,11552,22408,43487,
%T A065494 84378,163725,317700,616444,1196172,2321007,4503704,8738921,16956954,
%U A065494 32903164,63845000,123884479,240384374,466440273,905077080,1756205088
%N A065494 Number of (binary) bit strings in which no even length block of 0's is 
               followed by an even length block of 1's.
%F A065494 O.g.f.: (1+x)^2/(1-3x^2-2x^3+x^4)
%e A065494 a(6)=64-7=57 because 000011, 001111, 001100, 001101, 100110, 010011, 
               110011 are forbidden.
%Y A065494 Cf. A061279 (forbids odd block 0's - odd block 1's), A065455, A065495, 
               A065497.
%Y A065494 Sequence in context: A026023 A077596 A091865 this_sequence A134044 A079967 
               A018088
%Y A065494 Adjacent sequences: A065491 A065492 A065493 this_sequence A065495 A065496 
               A065497
%K A065494 nonn
%O A065494 0,2
%A A065494 Len Smiley (smiley(AT)math.uaa.alaska.edu), Nov 24 2001