thus Sum (digits (3040,10)) = (Sum <%0,4,0%>) + (Sum <%3%>) by Th632, AFINSQ_2:55
.= ((Sum <%0,4%>) + (Sum <%0%>)) + (Sum <%3%>) by AFINSQ_2:55
.= ((0 + 4) + (Sum <%0%>)) + (Sum <%3%>) by AFINSQ_2:54
.= ((0 + 4) + 0) + (Sum <%3%>) by AFINSQ_2:53
.= 4 + 3 by AFINSQ_2:53
.= 7 ; :: thesis: verum