
theorem Th266:
Sum digits(476,10) = 17
proof
  thus Sum digits(476,10) = Sum <%6,7%>+Sum <%4%> by Th265,AFINSQ_2:55
  .= (6 + 7) + Sum <%4%> by AFINSQ_2:54
  .= 13 + 4 by AFINSQ_2:53
  .= 17;
end;
