We're told Alan had a heart attack while he was playing hockey with his 19-year-old son, Carter. He was transported to Providence St. Joseph's Medical Center around noon today, and pronounced dead there. Law enforcement sources tell us ... a company that recovers organs was contacted, so some of Thicke's organs could be donated. He's survived by his 3 sons -- Robin, Brennan and Carter ... and his wife, Tanya. The Canadian born actor was most famous for his role as Jason Seaver, the dad on the '80s sitcom, "Growing Pains." Most recently, he was on the Netflix reboot, "Fuller...