table (+,+,+,max)
pp(Row,_Column,Tri,Sum),Row>Tri.length => Sum=0.
pp(Row,Column,Tri,Sum) ?=>
  pp(Row+1,Column,Tri,Sum1),
  Sum = Sum1+Tri[Row,Column].
pp(Row,Column,Tri,Sum) =>
  pp(Row+1,Column+1,Tri,Sum1),
  Sum = Sum1+Tri[Row,Column].