thus Sum (digits (2288,10)) = (Sum <%8,8,2%>) + (Sum <%2%>) by Th908, AFINSQ_2:55
.= ((Sum <%8,8%>) + (Sum <%2%>)) + (Sum <%2%>) by AFINSQ_2:55
.= ((8 + 8) + (Sum <%2%>)) + (Sum <%2%>) by AFINSQ_2:54
.= ((8 + 8) + 2) + (Sum <%2%>) by AFINSQ_2:53
.= 18 + 2 by AFINSQ_2:53
.= 20 ; :: thesis: verum