23=4×5+3
27=4×6+3
30=4×7+3
.
303=4×75+3
n=4×x+3(x=de cate ori se include 4 in n)
nr termeni=75-4-1=70 termeni
S=70×3+4(5+6+7+...+75)
5+6+7+...+75=75×76/2-1-2-3-4-0
=2850-10
=2840
S=210+4×2840
S=11570
