Răspuns :
d:6=r+3 si r => d=6*(r+3)+r => d=6r+18+r => d=7r+18
stim ca: r < 6 => r={1;2;3;4;5} =>
d=6*(1+3)+1 => d=6*4+1 => d=24+1 => d=25
d=6*(2+3)+2 => d=6*5+2 => d=30+2 =>d=32
d=6*(3+3)+3 => d=6*6+3 => d=36+3 => d=39
d=6*(4+3)+4 =>d=6*7+4 => d=42+4 =>d=46
d=6*(5+3)+5 =>d=6*8+5 => d=48+5 => d=53
S=25+32+39+46+53
S=57+85+53
S=142+53
S=195
=> n : 6 = r+3 (rest r) => n = 6*(r+3)+r = 7r+18 resturile posibile sunt: 0;1;2;3;4;5;6
n = { 7*0+18=18 ; 7*1+18=25 ; 7*2+18=32 ; 7*3+18=39 ;
7*4+18=46 ; 7*5+18=53 }
S(n) = 18 + 25 + 32 + 39 + 46 + 53 = 213