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 A104566 #12 Aug 20 2017 09:34:33 %S A104566 1,3,2,4,3,1,6,5,3,2,7,6,4,3,1,9,8,6,5,3,2,10,9,7,6,4,3,1,12,11,9,8,6, %T A104566 5,3,2,13,12,10,9,7,6,4,3,1,15,14,12,11,9,8,6,5,3,2,16,15,13,12,10,9, %U A104566 7,6,4,3,1,18,17,15,14,12,11,9,8,6,5,3,2,19,18,16,15,13,12,10,9,7,6,4,3,1 %N A104566 Triangle read by rows: T(i,j) is the (i,j)-entry (1 <= j <= i) of the product H*R of the infinite lower triangular matrices H = [1; 1,2; 1,2,1; 1 2,1,2; ...] and R = [1; 1,1; 1,1,1; 1,1,1,1; ...]. %F A104566 For 1 <= j <= i: T(i,j) = 3(i-j+1)/2 if i and j are of opposite parity; T(i,j) = 3(i-j)/2 + 1 if both i and j are odd; T(i,j) = 3(i-j)/2 + 2 if both i and j are even. - _Emeric Deutsch_, Mar 24 2005 %e A104566 The first few rows are %e A104566 1; %e A104566 3, 2; %e A104566 4, 3, 1; %e A104566 6, 5, 3, 2; %e A104566 ... %p A104566 T:=proc(i,j) if j>i then 0 elif i mod 2 = 1 and j mod 2 = 1 then 3*(i-j)/2+1 elif i mod 2 = 0 and j mod 2 = 0 then 3*(i-j)/2+2 elif i+j mod 2 = 1 then 3*(i-j+1)/2 else fi end: for i from 1 to 14 do seq(T(i,j),j=1..i) od; # yields sequence in triangular form # _Emeric Deutsch_, Mar 24 2005 %Y A104566 Row sums yield A001082. %Y A104566 Columns 1, 3, 5, ... (starting at the diagonal entry) yield A032766. %Y A104566 Columns 2, 4, 6, ... (starting at the diagonal entry) yield A045506. %Y A104566 Row sums = 1, 5, 8, 16, 21, ... (generalized octagonal numbers, A001082). A006578(2n-1) = A001082(2n). %K A104566 nonn,tabl %O A104566 1,2 %A A104566 _Gary W. Adamson_, Mar 15 2005 %E A104566 More terms from _Emeric Deutsch_, Mar 24 2005