thus Sum (digits (2440,10)) = (Sum <%0,4,4%>) + (Sum <%2%>) by Th572, AFINSQ_2:55
.= ((Sum <%0,4%>) + (Sum <%4%>)) + (Sum <%2%>) by AFINSQ_2:55
.= ((0 + 4) + (Sum <%4%>)) + (Sum <%2%>) by AFINSQ_2:54
.= ((0 + 4) + 4) + (Sum <%2%>) by AFINSQ_2:53
.= 8 + 2 by AFINSQ_2:53
.= 10 ; :: thesis: verum