16 9 3 15 3 20 6 { 20 8 5 14 21 13 2 5 18 19 13 1 19 15 14 }

This is probably a number to letter mapping, in the form of
1->A, 2->B, 3->C, 4->D, ...

Translation:
p i c o c t f { t h e n u m b e r s m a s o n }

Flag:
picoCTF{thenumbersmason}