Harshad or Niven series: Difference between revisions

=={{header|Maxima}}==

<syntaxhighlight lang="maxima">

/* Function that returns a list of digits given a nonnegative integer */

decompose(num) := block([digits, remainder],

digits: [],

while num > 0 do

(remainder: mod(num, 10),

digits: cons(remainder, digits),

num: floor(num/10)),

digits

)$

/* Function that returns a list of the first len Harshad numbers */

harshad_count(len):=block(

[i:1,count:0,result:[]],

while count<len do (if map(lambda([x],if mod(x,apply("+",decompose(x)))=0 then true),[i])=[true] then (result:endcons(i,result),count:count+1),i:i+1),

result)$

/* Function that returns a list of the Harshad numbers up to len */

first_count(len):=block(

[i:1,count:0,result:[]],

while i<=len do (if map(lambda([x],if mod(x,apply("+",decompose(x)))=0 then true),[i])=[true] then (result:endcons(i,result),count:count+1),i:i+1),

length(result))$

/* Test cases */

harshad_count(20);

block(first_count(1000),last(harshad_count(%%+1)));

</syntaxhighlight>

{{out}}

<pre>

[1,2,3,4,5,6,7,8,9,10,12,18,20,21,24,27,30,36,40,42]

1002

</pre>