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 A213833 #10 Feb 27 2018 10:27:25 %S A213833 1,7,3,24,17,5,58,48,27,7,115,102,72,37,9,201,185,146,96,47,11,322, %T A213833 303,255,190,120,57,13,484,462,405,325,234,144,67,15,693,668,602,507, %U A213833 395,278,168,77,17,955,927,852,742,609,465 %N A213833 Rectangular array: (row n) = b**c, where b(h) = 3*h-2, c(h) = 2*n-3+2*h, n>=1, h>=1, and ** = convolution. %C A213833 Principal diagonal: A103748. %C A213833 Antidiagonal sums: A213834. %C A213833 Row 1, (1,3,5,7,...)**(1,3,5,7,...): A081436. %C A213833 Row 2, (1,3,5,7,...)**(3,5,7,9,...): A144640. %C A213833 Row 3, (1,3,5,7,...)**(5,7,9,11,...): (2*k^3 + 11*k^2 - 3*k)/2. %C A213833 For a guide to related arrays, see A212500. %H A213833 Clark Kimberling, <a href="/A213833/b213833.txt">Antidiagonals n = 1..12, flattened</a> %F A213833 T(n,k) = 4*T(n,k-1)-6*T(n,k-2)+4*T(n,k-3)-T(n,k-4). %F A213833 G.f. for row n: f(x)/g(x), where f(x) = x*((2*n-1) + (2*n+1)*x - (4*n-6)*x^2) and g(x) = (1-x)^4. %e A213833 Northwest corner (the array is read by falling antidiagonals): %e A213833 1....7....24....58....115 %e A213833 3....17...48....102...185 %e A213833 5....27...72....146...255 %e A213833 7....37...96....190...325 %e A213833 9....47...120...234...395 %e A213833 11...57...144...278...465 %t A213833 b[n_]:=3n-2;c[n_]:=2n-1; %t A213833 t[n_,k_]:=Sum[b[k-i]c[n+i],{i,0,k-1}] %t A213833 TableForm[Table[t[n,k],{n,1,10},{k,1,10}]] %t A213833 Flatten[Table[t[n-k+1,k],{n,12},{k,n,1,-1}]] %t A213833 r[n_]:=Table[t[n,k],{k,1,60}] (* A213833 *) %t A213833 Table[t[n,n],{n,1,40}] (* A130748 *) %t A213833 s[n_]:=Sum[t[i,n+1-i],{i,1,n}] %t A213833 Table[s[n],{n,1,50}] (* A213834 *) %Y A213833 Cf. A212500. %K A213833 nonn,tabl,easy %O A213833 1,2 %A A213833 _Clark Kimberling_, Jul 04 2012