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 A158906 #13 Jan 08 2015 15:21:32 %S A158906 1,2,1,3,0,1,4,1,0,1,5,0,0,0,1,6,1,1,0,0,1,7,0,0,0,0,0,1,8,1,0,1,0,0, %T A158906 0,1,9,0,1,0,0,0,0,0,1,10,1,0,0,1,0,0,0,0,1,11,0,0,0,0,0,0,0,0,0,1,12, %U A158906 1,1,1,0,1,0,0,0,0,0,1 %N A158906 Triangle read by rows: the matrix product A158821 * A051731. %F A158906 Triangle read by rows, A158821 * A051731, where A051731 = the inverse Mobius transform. %F A158906 T(n,k) = A051731(n,k) if k>1. %F A158906 T(n,1) = n. %e A158906 First few rows of the triangle = %e A158906 1; %e A158906 2, 1; %e A158906 3, 0, 1; %e A158906 4, 1, 0, 1; %e A158906 5, 0, 0, 0, 1; %e A158906 6, 1, 1, 0, 0, 1; %e A158906 7, 0, 0, 0, 0, 0, 1; %e A158906 8, 1, 0, 1, 0, 0, 0, 1; %e A158906 9, 0, 1, 0, 0, 0, 0, 0, 1; %e A158906 10, 1, 0, 0, 1, 0, 0, 0, 0, 1; %e A158906 11, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1; %e A158906 12, 1, 1, 1, 0, 1, 0, 0, 0, 0, 0, 1; %e A158906 13, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1; %e A158906 ... %p A158906 N:= 20: # to get the first N rows %p A158906 M1:= Matrix(N,N, shape = triangular[lower]); %p A158906 M1[..,1] := Vector([$0..N-1]); %p A158906 M1:= M1 + LinearAlgebra:-IdentityMatrix(N); %p A158906 M2:= Matrix(N,N, shape=triangular[lower],(i,j) -> charfcn[0](i mod j)); %p A158906 M:= M1 . M2; %p A158906 seq(seq(M[i,j],j=1..i),i=1..N); # _Robert Israel_, Jan 08 2015 %Y A158906 Cf. A158821, A051731, A158907 (row sums). %K A158906 nonn,tabl %O A158906 1,2 %A A158906 _Gary W. Adamson_ and _Mats Granvik_, Mar 29 2009