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 A090171 #14 Oct 27 2021 15:02:37 %S A090171 0,1,0,1,1,0,0,1,0,0,1,1,1,1,0,1,1,1,1,1,0,0,0,1,1,0,0,0,1,0,0,1,0,0, %T A090171 1,0,1,1,1,1,1,1,1,1,0,0,1,1,1,1,1,1,1,0,0,1,1,1,1,1,1,1,1,1,1,0,1,1, %U A090171 0,1,1,1,1,1,0,1,1,0,0,0,0,0,1,1,1,1,0,0,0,0,0,1,0,0,0,1,1,1,1,1,0,0,0,1,0 %N A090171 Triangle read by rows, related to Pascal's triangle read mod 2, starting with 0, 1, 0. %H A090171 Y. Moshe, <a href="http://dx.doi.org/10.1016/S0022-314X(03)00103-3">The density of 0's in recurrence double sequences</a>, J. Number Theory, 103 (2003), 109-121; see Fig. 2. %F A090171 T(n, k) = T(n-1, k) + T(n-1, k-1) + T(n-2, k) + T(n-2, k-1) + T(n-2, k-2) for n >= 2, k >= 0, with initial conditions specified by first two rows. %e A090171 Triangle begins: %e A090171 0 %e A090171 1 0 %e A090171 1 1 0 %e A090171 0 1 0 0 %e A090171 1 1 1 1 0 %e A090171 ... %Y A090171 Cf. A007318, A083093. %Y A090171 Cf. A090172, A090173, A090174, A091533, A091562, A205575 (same recurrence). %Y A090171 a(n, k) = A090174(n-1, k), k<n, 0 otherwise. %K A090171 nonn,easy,tabl %O A090171 0,1 %A A090171 _N. J. A. Sloane_, Jan 19 2004 %E A090171 Edited and extended by _Christian G. Bower_, Jan 20 2004