thus Sum (digits (2240,10)) = (Sum <%0,4,2%>) + (Sum <%2%>) by Th552, AFINSQ_2:55
.= ((Sum <%0,4%>) + (Sum <%2%>)) + (Sum <%2%>) by AFINSQ_2:55
.= ((0 + 4) + (Sum <%2%>)) + (Sum <%2%>) by AFINSQ_2:54
.= ((0 + 4) + 2) + (Sum <%2%>) by AFINSQ_2:53
.= 6 + 2 by AFINSQ_2:53
.= 8 ; :: thesis: verum