%I #3 Oct 31 2015 15:16:45
%S 1,2,4,8,15,30,57,112,216,420,815,1580,3069,5950,11552,22408,43487,
%T 84378,163725,317700,616444,1196172,2321007,4503704,8738921,16956954,
%U 32903164,63845000,123884479,240384374,466440273,905077080,1756205088
%N Number of (binary) bit strings in which no even length block of 0's is followed by an even length block of 1's.
%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,3,2,1).
%F O.g.f.: (1+x)^2/(13x^22x^3+x^4)
%e a(6)=647=57 because 000011, 001111, 001100, 001101, 100110, 010011, 110011 are forbidden.
%Y Cf. A061279 (forbids odd block 0's  odd block 1's), A065455, A065495, A065497.
%K nonn,easy
%O 0,2
%A _Len Smiley_, Nov 24 2001
