153+4x0=153
153+4x1=157
153+4x2=161 ...............153+4x296 =1337
a) 296+1=297 termeni
b) 153+4x43=325
c) 153+4x44=329 .................. 153+4x81=477
nr termeni 81-44+1=38
153x38=5814
4x44=176
4x45=180.................4x81=324
176+180+......324=4(44+45+....81)=4x19x125=9500
5814+9500=15314