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 A213753 #12 Jul 11 2012 08:51:12 %S A213753 1,6,3,21,16,7,58,51,36,15,141,132,111,76,31,318,307,280,231,156,63, %T A213753 685,672,639,576,471,316,127,1434,1419,1380,1303,1168,951,636,255, %U A213753 2949,2932,2887,2796,2631,2352,1911,1276,511,5998,5979,5928,5823 %N A213753 Rectangular array: (row n) = b**c, where b(h) = 2*h-1, c(h) = -1 + 2^(n-1+h), n>=1, h>=1, and ** = convolution. %C A213753 Principal diagonal: A213754. %C A213753 Antidiagonal sums: A213755. %C A213753 Row 1, (1,3,5,7,9,...)**(1,3,7,15,...): A047520. %C A213753 Row 2, (1,3,5,7,9,...)**(3,7,15,31,...). %C A213753 Row 3, (1,3,5,7,9,...)**(7,15,31,63...). %C A213753 Ror a guide to related arrays, see A213500. %H A213753 Clark Kimberling, <a href="/A213753/b213753.txt">Antidiagonals n = 1..60, flattened</a> %F A213753 T(n,k) = 5*T(n,k-1)-9*T(n,k-2)+7*T(n,k-3)-2*T(n,k-4). %F A213753 G.f. for row n: f(x)/g(x), where f(x) = x*(-1 + 2^n + x + (-2 + 2^n)*x^2) and g(x) = (1 - 2*x)(1 - x )^3. %e A213753 Northwest corner (the array is read by falling antidiagonals): %e A213753 1....6.....21....58.....141 %e A213753 3....16....51....132....307 %e A213753 7....36....111...280....639 %e A213753 15...76....231...576....1303 %e A213753 31...156...471...1168...2631 %t A213753 b[n_] := 2 n - 1; c[n_] := -1 + 2^n; %t A213753 t[n_, k_] := Sum[b[k - i] c[n + i], {i, 0, k - 1}] %t A213753 TableForm[Table[t[n, k], {n, 1, 10}, {k, 1, 10}]] %t A213753 Flatten[Table[t[n - k + 1, k], {n, 12}, {k, n, 1, -1}]] %t A213753 r[n_] := Table[t[n, k], {k, 1, 60}] (* A213753 *) %t A213753 Table[t[n, n], {n, 1, 40}] (* A213754 *) %t A213753 s[n_] := Sum[t[i, n + 1 - i], {i, 1, n}] %t A213753 Table[s[n], {n, 1, 50}] (* A213755 *) %Y A213753 Cf. A213500. %K A213753 nonn,tabl,easy %O A213753 1,2 %A A213753 _Clark Kimberling_, Jun 20 2012