demo/sumcon.dem

   1 gensumindex:0$
   2 y:sum(a[i]*x^i,i,0,inf);
   3 y1:diff(y,x);
   4 y2:diff(y1,x);
   5 (x^2+1)*y2+3*x*y1+2*y;
   6 expand(%);
   7 factor(%);
   8 intosum(%)$
   9 bashindices(%);
  10 changevar(%,(j4-2)-j,j,j4);
  11 niceindices(%);
  12 sumcontract(%);
  13 factor(%);
  14 part(%,1);
  15 %/x^i=0;
  16 solve(%,a[i+2]);