/* Predicate function that checks wether a positive integer is arithmetic or not */
arith_nump(n):=block(listify(divisors(n)),apply("+",%%)/length(%%),if integerp(%%) then true)$

/* Function that returns a list of the first len arithmetic numbers */
arith_num_count(len):=block(
    [i:1,count:0,result:[]],
    while count<len do (if arith_nump(i) then (result:endcons(i,result),count:count+1),i:i+1),
    result)$

/* Test cases */
/* First 100 arithmetic numbers */
arith_num_count(100);

/* The 1000th arithmetic number */
last(arith_num_count(1000));

/* The 10000th arithmetic number */
last(arith_num_count(10000));

/* Number of composites among the first 1000 arithmetic numbers */
block(rest(arith_num_count(1000)),sublist(%%,lambda([x],primep(x)=false)),length(%%));

/* Number of composites among the first 10000 arithmetic numbers */
block(rest(arith_num_count(10000)),sublist(%%,lambda([x],primep(x)=false)),length(%%));