thus Sum (digits (2244,10)) = (Sum <%4,4,2%>) + (Sum <%2%>) by Th904, AFINSQ_2:55
.= ((Sum <%4,4%>) + (Sum <%2%>)) + (Sum <%2%>) by AFINSQ_2:55
.= ((4 + 4) + (Sum <%2%>)) + (Sum <%2%>) by AFINSQ_2:54
.= ((4 + 4) + 2) + (Sum <%2%>) by AFINSQ_2:53
.= 10 + 2 by AFINSQ_2:53
.= 12 ; :: thesis: verum