thus Sum (digits (1694,10)) = (Sum <%4,9,6%>) + (Sum <%1%>) by Th860, AFINSQ_2:55
.= ((Sum <%4,9%>) + (Sum <%6%>)) + (Sum <%1%>) by AFINSQ_2:55
.= ((4 + 9) + (Sum <%6%>)) + (Sum <%1%>) by AFINSQ_2:54
.= ((4 + 9) + 6) + (Sum <%1%>) by AFINSQ_2:53
.= 19 + 1 by AFINSQ_2:53
.= 20 ; :: thesis: verum