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 A213838 #11 Jul 11 2012 04:30:23 %S A213838 1,8,3,29,20,5,72,59,32,7,145,128,89,44,9,256,235,184,119,56,11,413, %T A213838 388,325,240,149,68,13,624,595,520,415,296,179,80,15,897,864,777,652, %U A213838 505,352,209,92,17,1240,1203,1104,959,784 %N A213838 Rectangular array: (row n) = b**c, where b(h) = 4*h-3, c(h) = 2*n-3+2*h, n>=1, h>=1, and ** = convolution. %C A213838 Principal diagonal: A213839. %C A213838 Antidiagonal sums: A213840. %C A213838 Row 1, (1,5,9,13,...)**(1,3,5,7,...): A100178. %C A213838 Row 2, (1,5,9,13,...)**(3,5,7,9,...): (4*k^3 + 9*k^2 - 4*k)/3. %C A213838 Row 3, (1,5,9,13,...)**(5,7,9,11,...): (4*k^3 + 21*k^2 - 10*k)/3. %C A213838 For a guide to related arrays, see A212500. %H A213838 Clark Kimberling, <a href="/A213838/b213838.txt">Antidiagonals n = 1..60, flattened</a> %F A213838 T(n,k) = 4*T(n,k-1)-6*T(n,k-2)+4*T(n,k-3)-T(n,k-4). %F A213838 G.f. for row n: f(x)/g(x), where f(x) = x*(2*n-1 + 4*n*x - (6*n-9)*x^2) and g(x) = (1-x)^4. %e A213838 Northwest corner (the array is read by falling antidiagonals): %e A213838 1....8....29....72....145 %e A213838 3....20...59....128...235 %e A213838 5....32...89....184...325 %e A213838 7....44...119...240...415 %e A213838 9....56...149...296...505 %e A213838 11...68...179...352...595 %t A213838 b[n_]:=4n-3; c[n_]:=2n-1; %t A213838 t[n_,k_]:=Sum[b[k-i]c[n+i],{i,0,k-1}] %t A213838 TableForm[Table[t[n,k],{n,1,10},{k,1,10}]] %t A213838 Flatten[Table[t[n-k+1,k],{n,12},{k,n,1,-1}]] %t A213838 r[n_]:=Table[t[n,k],{k,1,60}] (* A213838 *) %t A213838 Table[t[n,n],{n,1,40}] (* A213839 *) %t A213838 s[n_]:=Sum[t[i,n+1-i],{i,1,n}] %t A213838 Table[s[n],{n,1,50}] (* A213840 *) %Y A213838 Cf. A212500. %K A213838 nonn,tabl,easy %O A213838 1,2 %A A213838 _Clark Kimberling_, Jul 05 2012