1+3+5+... benchmark

source code being benchmarked: https://pastebin.com/KLveRw2P

the benchmark:

braden[6][pts11][~]$ gcc odds.c && ./a.out
3136
3136
3136
braden[6][pts11][~]$ gcc odds.c -DTEST=2 && time ./a.out

real    0m0.001s
user    0m0.000s
sys     0m0.000s
braden[6][pts11][~]$ gcc odds.c -DTEST=3 && time ./a.out

real    0m5.313s
user    0m5.308s
sys     0m0.000s
braden[6][pts11][~]$ gcc odds.c -DTEST=4 && time ./a.out

real    0m8.334s
user    0m8.332s
sys     0m0.000s