reserve a,b,n for Element of NAT;

theorem
  for a,n being Element of NAT holds GenFib(2*a+1,2*a+1,n+1) = (2*a+1) *
  Fib(n+2)
proof
  let a,n be Element of NAT;
  GenFib(2*a+1,2*a+1,n+1)=(2*a+1)*Fib(n)+(2*a+1)*Fib(n+1) by Th49
    .= (2*a+1)*(Fib(n)+Fib(n+1))
    .= (2*a+1)*Fib(n+2) by FIB_NUM2:24;
  hence thesis;
end;
