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 A065494 #3 Oct 31 2015 15:16:45 %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. %H A065494 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (0,3,2,-1). %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. %K A065494 nonn,easy %O A065494 0,2 %A A065494 _Len Smiley_, Nov 24 2001