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 A213836 #8 Jul 10 2012 19:30:13 %S A213836 1,7,2,22,13,3,50,37,19,4,95,78,52,25,5,161,140,106,67,31,6,252,227, %T A213836 185,134,82,37,7,372,343,293,230,162,97,43,8,525,492,434,359,275,190, %U A213836 112,49,9,715,678,612,525,425,320,218,127 %N A213836 Rectangular array: (row n) = b**c, where b(h) = 4*h-3, c(h) = n-1+h, n>=1, h>=1, and ** = convolution. %C A213836 Principal diagonal: A213837. %C A213836 Antidiagonal sums: A071238. %C A213836 Row 1, (1,5,9,13,...)**(1,2,3,4,...): A002412. %C A213836 Row 2, (1,5,9,13,...)**(2,3,4,5,...): (4*k^3 + 15*k^2 - 7*k)/6. %C A213836 Row 3, (1,5,9,13,...)**(3,4,5,6,...): (4*k^3 + 27*k^2 - 13*k)/6. %C A213836 For a guide to related arrays, see A212500. %H A213836 Clark Kimberling, <a href="/A213836/b213836.txt">Antidiagonals n = 1..60, flattened</a> %F A213836 T(n,k) = 4*T(n,k-1)-6*T(n,k-2)+4*T(n,k-3)-T(n,k-4). %F A213836 G.f. for row n: f(x)/g(x), where f(x) = x*(n + (2*n+1)*x - 3*(n-1)*x^2) and g(x) = (1-x)^4. %e A213836 Northwest corner (the array is read by falling antidiagonals): %e A213836 1...7....22...50....95 %e A213836 2...13...37...78....140 %e A213836 3...19...52...106...185 %e A213836 4...25...67...134...230 %e A213836 5...31...82...162...275 %e A213836 6...37...97...190...320 %t A213836 b[n_]:=4n-3;c[n_]:=n; %t A213836 t[n_,k_]:=Sum[b[k-i]c[n+i],{i,0,k-1}] %t A213836 TableForm[Table[t[n,k],{n,1,10},{k,1,10}]] %t A213836 Flatten[Table[t[n-k+1,k],{n,12},{k,n,1,-1}]] %t A213836 r[n_]:=Table[t[n,k],{k,1,60}] (* A213836 *) %t A213836 Table[t[n,n],{n,1,40}] (* A213837 *) %t A213836 s[n_]:=Sum[t[i,n+1-i],{i,1,n}] %t A213836 Table[s[n],{n,1,50}] (* A071238 *) %Y A213836 Cf. A212500. %K A213836 nonn,tabl,easy %O A213836 1,2 %A A213836 _Clark Kimberling_, Jul 04 2012