Если будет несуществующий индекс, то равно nil?

Да.

Добавлено через 11 минут
Города существ, нейтралы отсутствуют, т.к. у них нет города.

towns = {[1]=0, [2]=0, [3]=0, [4]=0, [5]=0, [6]=0, [7]=0, [8]=0, [9]=0, [10]=0, [11]=0, [12]=0, [13]=0, [14]=0, [15]=5, [16]=5, [17]=5, [18]=5, [19]=5, [20]=5, [21]=5, [22]=5, [23]=5, [24]=5, [25]=5, [26]=5, [27]=5, [28]=5, [29]=4, [30]=4, [31]=4, [32]=4, [33]=4, [34]=4, [35]=4, [36]=4, [37]=4, [38]=4, [39]=4, [40]=4, [41]=4, [42]=4, [43]=1, [44]=1, [45]=1, [46]=1, [47]=1, [48]=1, [49]=1, [50]=1, [51]=1, [52]=1, [53]=1, [54]=1, [55]=1, [56]=1, [57]=2, [58]=2, [59]=2, [60]=2, [61]=2, [62]=2, [63]=2, [64]=2, [65]=2, [66]=2, [67]=2, [68]=2, [69]=2, [70]=2, [71]=3, [72]=3, [73]=3, [74]=3, [75]=3, [76]=3, [77]=3, [78]=3, [79]=3, [80]=3, [81]=3, [82]=3, [83]=3, [84]=3, [92]=6, [93]=6, [94]=6, [95]=6, [96]=6, [97]=6, [98]=6, [99]=6, [100]=6, [101]=6, [102]=6, [103]=6, [104]=6, [105]=6, [106]=0, [107]=0, [108]=0, [109]=0, [110]=0, [111]=0, [112]=0, [117]=7, [118]=7, [119]=7, [120]=7, [121]=7, [122]=7, [123]=7, [124]=7, [125]=7, [126]=7, [127]=7, [128]=7, [129]=7, [130]=7, [131]=5, [132]=5, [133]=5, [134]=5, [135]=5, [136]=5, [137]=5, [138]=3, [139]=3, [140]=3, [141]=3, [142]=3, [143]=3, [144]=3, [145]=1, [146]=1, [147]=1, [148]=1, [149]=1, [150]=1, [151]=1, [152]=4, [153]=4, [154]=4, [155]=4, [156]=4, [157]=4, [158]=4, [159]=2, [160]=2, [161]=2, [162]=2, [163]=2, [164]=2, [165]=2, [166]=6, [167]=6, [168]=6, [169]=6, [170]=6, [171]=6, [172]=6, [173]=7, [174]=7, [175]=7, [176]=7, [177]=7, [178]=7, [179]=7, [326]=2, [327]=3, [328]=6, [329]=0, [330]=5, [331]=4, [332]=7, [333]=1, [334]=2, [335]=3, [336]=6, [337]=0, [338]=5, [339]=4, [340]=7, [341]=1, [342]=2, [343]=3, [344]=6, [345]=0, [346]=5, [347]=4, [348]=7, [349]=1, [350]=2, [351]=3, [352]=6, [353]=0, [354]=5, [355]=4, [356]=7, [357]=1, [358]=2, [359]=3, [360]=6, [361]=0, [362]=5, [363]=4, [364]=7, [365]=1, [366]=2, [367]=3, [368]=6, [369]=0, [370]=5, [371]=4, [372]=7, [373]=1, [374]=2, [375]=3, [376]=6, [377]=0, [378]=5, [379]=4, [380]=7, [381]=1, [460]=4, [606]=0, [604]=0, [603]=0, [600]=0, [602]=0, [601]=0, [605]=0, [609]=4}