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 A113290 #4 Mar 30 2012 18:36:51 %S A113290 0,2,0,-3,0,0,6,4,4,0,-10,-10,-10,0,0,19,24,30,12,6,0,-35,-49,-70,-42, %T A113290 -21,0,0,72,104,164,128,84,24,8,0,-150,-216,-360,-324,-252,-108,-36,0, %U A113290 0,343,480,820,800,710,400,180,40,10,0,-803,-1089,-1870,-1892,-1826,-1210,-660,-220,-55,0,0 %N A113290 Matrix logarithm of triangle A113287. %F A113290 T(n, 1) = (n+1)*A113291(n). %e A113290 Triangle begins: %e A113290 0; %e A113290 2,0; %e A113290 -3,0,0; %e A113290 6,4,4,0; %e A113290 -10,-10,-10,0,0; %e A113290 19,24,30,12,6,0; %e A113290 -35,-49,-70,-42,-21,0,0; %e A113290 72,104,164,128,84,24,8,0; %e A113290 -150,-216,-360,-324,-252,-108,-36,0,0; %e A113290 343,480,820,800,710,400,180,40,10,0; ... %o A113290 (PARI) {T(n,k)=local(x=X+O(X^(n+2)),y=Y+O(Y^(n+2)),M=matrix(n+1,n+1,r,c,if(r==c,1, if(r>c,r*polcoeff(polcoeff(1/(1-x*y)+x/((1-x*y)*(1+x+x*y)),r-1,X),c-1,Y))))); if(n<k,0,(sum(j=1,n+1,-(M^0-M)^j/j))[n+1,k+1])} %Y A113290 Cf. A113287, A113288, A113291 (column 1), A113292 (column 0), A072374. %K A113290 sign,tabl %O A113290 0,2 %A A113290 _Paul D. Hanna_, Oct 23 2005