Happy Numbers in C

happyNumbers.c

//2014-02-10 jorge@jorgechamorro.com     happy numbers in C

#include<stdio.h>

unsigned sumaCuadrados (unsigned n) {
  unsigned d, r= 0;
  while (n) d= n % 10, r+= d*d, n/= 10;
  return r;
}

int isHappy (unsigned n) {
  while (n && n!=1 && n!=4 && n!=16 && n!=37 && n!=58 && n!=89 && n!=145 && n!=42 && n!=20)
    n= sumaCuadrados(n);
  return n == 1;
}

int main () {
  unsigned i, ctr= 0;
  for (i=0 ; i<10000000 ; i++) isHappy(i) && ctr++;
  printf("%d\n", ctr);
}