thus Sum (digits (1166,10)) = (Sum <%6,6,1%>) + (Sum <%1%>) by Th816, AFINSQ_2:55
.= ((Sum <%6,6%>) + (Sum <%1%>)) + (Sum <%1%>) by AFINSQ_2:55
.= ((6 + 6) + (Sum <%1%>)) + (Sum <%1%>) by AFINSQ_2:54
.= ((6 + 6) + 1) + (Sum <%1%>) by AFINSQ_2:53
.= 13 + 1 by AFINSQ_2:53
.= 14 ; :: thesis: verum