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 A079409 #4 Feb 18 2015 07:51:27 %S A079409 1,1,0,1,1,0,1,2,0,0,1,1,1,0,0,1,2,3,0,0,0,1,1,1,1,0,0,0,1,2,3,4,0,0, %T A079409 0,0,1,1,1,1,1,0,0,0,0,1,2,3,4,5,0,0,0,0,0,1,1,1,1,1,1,0,0,0,0,0,1,2, %U A079409 3,4,5,6,0,0,0,0,0,0,1,1,1,1,1,1,1,0,0,0,0,0,0,1,2,3,4,5,6,7,0,0,0,0,0,0,0 %N A079409 Array T(m,n) (m>=0, n>=0) read by antidiagonals: T(0, 0) = 1, T(0, n) = 0 if n > 0, T(m, n) = T(m-1, n - T(m-1, n)) + T(m-1, n - T(m-1, n-1)) if m > 0. %C A079409 This two-dimensional array is to Pascal's triangle as the Hofstadter Q-sequence A005185 is to Fibonacci's sequence. %C A079409 Unlike the Hofstadter Q-sequence, it is very regular and admits a simple closed form: T(m, n) = 0 if n > m, T(m, n) = 1 if n <= m and m - n is even, T(m, n) = n + 1 if n <= m and m - n is odd. %e A079409 For 0 <= m <= 6 and 0 <= n <= 6, the array looks like: %e A079409 1,0,0,0,0,0,0 %e A079409 1,1,0,0,0,0,0 %e A079409 1,2,1,0,0,0,0 %e A079409 1,1,3,1,0,0,0 %e A079409 1,2,1,4,1,0,0 %e A079409 1,1,3,1,5,1,0 %e A079409 1,2,1,4,1,6,1 %Y A079409 Cf. A004001, A005185, A007318, A052553, A079408. %K A079409 nonn,tabl %O A079409 0,8 %A A079409 _Rob Arthan_, Jan 06 2003