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 A093662 #6 Mar 20 2013 06:44:31 %S A093662 1,1,1,1,0,1,1,1,2,1,1,0,0,0,1,1,1,0,0,2,1,1,0,1,0,2,0,1,1,1,2,1,5,2, %T A093662 4,1,1,0,0,0,0,0,0,0,1,1,1,0,0,0,0,0,0,2,1,1,0,1,0,0,0,0,0,2,0,1,1,1, %U A093662 2,1,0,0,0,0,5,2,4,1,1,0,0,0,1,0,0,0,2,0,0,0,1,1,1,0,0,2,1,0,0,5,2,0,0,4,1 %N A093662 Lower triangular matrix, read by rows, defined as the convergent of the concatenation of matrices using the iteration: M(n+1) = [[M(n),0*M(n)],[M(n),M(n)^2]], with M(0) = [1]. %C A093662 Row sums form A093663, where A093663(2^n) = A016121(n) for n>=0. The 2^n-th row converges to A093664, where A093664(2^n+1) = A016121(n) for n>=0. %e A093662 Let M(n) be the lower triangular matrix formed from the first 2^n rows. %e A093662 To generate M(3) from M(2), obtain the matrix square of M(2): %e A093662 [1,0,0,0]^2=[1,0,0,0] %e A093662 [1,1,0,0]...[2,1,0,0] %e A093662 [1,0,1,0]...[2,0,1,0] %e A093662 [1,1,2,1]...[5,2,4,1], %e A093662 then M(3) is formed by starting with M(2) and appending M(2) to the bottom left and M(2)^2 to the bottom right: %e A093662 [1], %e A093662 [1,1], %e A093662 [1,0,1], %e A093662 [1,1,2,1], %e A093662 .......... %e A093662 [1,0,0,0],[1], %e A093662 [1,1,0,0],[2,1], %e A093662 [1,0,1,0],[2,0,1], %e A093662 [1,1,2,1],[5,2,4,1]. %e A093662 Repeating this process converges to triangle A093662. %Y A093662 Cf. A016121, A093655, A093658, A093663, A093664. %K A093662 nonn,tabl %O A093662 1,9 %A A093662 _Paul D. Hanna_, Apr 08 2004