A cabtaxi number for a given is the smallest positive number which can be written as in different ways, with either or allowed to be negative integers. For example, 91 is the 2nd cabtaxi number since it can be expressed . The known cabtaxi numbers are 1, 91, 728, 2741256, 6017193, 1412774811, 11302198488, 137513849003496, 424910390480793000, listed in A047696 of Sloane's OEIS. Adding the restriction gives the definition for the taxicab numbers.