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 A170877 #9 Aug 22 2013 03:35:58 %S A170877 1,2,3,5,7,10,15,22,30,43,61,88,123,173,246,348,487,688,972,1371,1928, %T A170877 2714,3822,5387,7582,10681,15046,21194,29835,42009,59159,83305,117292, %U A170877 165170,232593,327530,461198,649431,914493,1287747,1813281,2553346,3595465 %N A170877 Number of binary words of length n with properties that there is no pair of adjacent 1's and no subword of the form X^4 for any string X. %C A170877 The subword 01010101 (corresponding to X = 01) for example cannot occur. %H A170877 Lars Blomberg, <a href="/A170877/b170877.txt">Table of n, a(n) for n = 0..43</a> %e A170877 a(3) = 5: 000, 001, 010, 100, 101. %e A170877 a(4) = 7: 0001, 0010, 0100, 1000, 0101, 1010, 1001. %Y A170877 Cf. A003410, A028445, A135491. %K A170877 nonn %O A170877 0,2 %A A170877 _Benjamin Chaffin_ and _N. J. A. Sloane_, Jan 07 2010 %E A170877 a(24)-a(42) from _Lars Blomberg_, Aug 22 2013