1+6+11......+2006+2011= 1+2011 + 6+2006+...=
2012+2012+...2012 decate ori?
cate nuimere avem?
avem (2011-1)/5+1 =2010/5+1=403 numere deci 403/2 perechi de numere
toatl suma tip gauss=2012*403/2=405 418
altfel
1=5*0+1
6=5*1+1
.........
2011=5*402+1
suma= 5(1+2+..+402) +1+1+..+1 de 403ori=5*402*403/2+403=5*201*403+403=
403(1005+1) =403*1006=405418