theorem
  for D being set, p,q,r be Element of D^omega holds
  FlattenSeq <% p,q,r %> = p ^ q ^ r
proof
  let D be set, p,q,r be Element of D^omega;
  consider g being BinOp of D^omega such that
A1: for d1,d2 being Element of D^omega holds g.(d1,d2) = d1^d2 and
A2: FlattenSeq <% p,q,r %> = g "**" <% p,q,r %> by Def10;
  thus FlattenSeq <% p,q,r %> = g.(g.(p,q),r) by A2,Th39
    .= g.(p,q) ^ r by A1
    .= p ^ q ^ r by A1;
end;
