thus Sum (digits (1144,10)) = (Sum <%4,4,1%>) + (Sum <%1%>) by Th814, AFINSQ_2:55
.= ((Sum <%4,4%>) + (Sum <%1%>)) + (Sum <%1%>) by AFINSQ_2:55
.= ((4 + 4) + (Sum <%1%>)) + (Sum <%1%>) by AFINSQ_2:54
.= ((4 + 4) + 1) + (Sum <%1%>) by AFINSQ_2:53
.= 9 + 1 by AFINSQ_2:53
.= 10 ; :: thesis: verum