thus Sum (digits (2354,10)) = (Sum <%4,5,3%>) + (Sum <%2%>) by Th914, AFINSQ_2:55
.= ((Sum <%4,5%>) + (Sum <%3%>)) + (Sum <%2%>) by AFINSQ_2:55
.= ((4 + 5) + (Sum <%3%>)) + (Sum <%2%>) by AFINSQ_2:54
.= ((4 + 5) + 3) + (Sum <%2%>) by AFINSQ_2:53
.= 12 + 2 by AFINSQ_2:53
.= 14 ; :: thesis: verum