write()

Writes binary data to the serial port. This data is sent as a byte or series of bytes; to send the characters representing the digits of a number use the Print() function instead.
Wire.write(value)
Wire.write(string)
Wire.write(data, length)
value a value to send as a single byte
string a value to send as a series of bytes
data an array to send as bytes length the number of bytes to transmit
byte: write() will return the number of bytes written, though reading that number is optional
#include "Wire.h"

byte val = 0;

void setup() {
  Wire.begin(); // join i2c bus
}

void loop() {
  Wire.beginTransmission(44); // transmit to device #44 (0x2c)
                              // device address is specified in datasheet
  Wire.write(val);            // sends value byte  
  Wire.endTransmission();     // stop transmitting

  val++;           // increment value
  if (val == 64) { // if reached 64th position (max)
    val = 0;       // start over from lowest value
  }
  delay(500);
}