thus Sum (digits (2046,10)) = (Sum <%6,4,0%>) + (Sum <%2%>) by Th888, AFINSQ_2:55
.= ((Sum <%6,4%>) + (Sum <%0%>)) + (Sum <%2%>) by AFINSQ_2:55
.= ((6 + 4) + (Sum <%0%>)) + (Sum <%2%>) by AFINSQ_2:54
.= ((6 + 4) + 0) + (Sum <%2%>) by AFINSQ_2:53
.= 10 + 2 by AFINSQ_2:53
.= 12 ; :: thesis: verum