thus Sum (digits (1940,10)) = (Sum <%0,4,9%>) + (Sum <%1%>) by Th522, AFINSQ_2:55
.= ((Sum <%0,4%>) + (Sum <%9%>)) + (Sum <%1%>) by AFINSQ_2:55
.= ((0 + 4) + (Sum <%9%>)) + (Sum <%1%>) by AFINSQ_2:54
.= ((0 + 4) + 9) + (Sum <%1%>) by AFINSQ_2:53
.= 13 + 1 by AFINSQ_2:53
.= 14 ; :: thesis: verum