code: public ScriptBuilder smallNum(int index, int num) {
          checkArgument(num >= 0, "Cannot encode negative numbers with smallNum");
          checkArgument(num <= 16, "Cannot encode numbers larger than 16 with smallNum");
          return addChunk(index, new ScriptChunk(Script.encodeToOpN(num), null));
      }
docs: Adds the given number as a OP_N opcode to the given index in the program.
  Only handles values 0-16 inclusive.
  
  @see #number(long)