Problem Statement

The Harshad or Niven numbers are positive integers ≥ 1 that are divisible by the sum of their digits. For example,   42   is a Harshad number as   42   is divisible by   (4 + 2)   without remainder. Assume that the series is defined as the numbers in increasing order.

The task is to create a function/method/procedure to generate successive members of the Harshad sequence. Use it to:

Show your output here.

Let's start with the solution:

USING: math.text.utils lists lists.lazy ;

: niven? ( n -- ? ) dup 1 digit-groups sum mod 0 = ;

: first-n-niven ( n -- seq )
    1 lfrom [ niven? ] lfilter ltake list>array ;

: next-niven ( n -- m ) 1 + [ dup niven? ] [ 1 + ] until ;

20 first-n-niven .
1000 next-niven .