sidef-scripts/Math/armstrong_numbers.sf

#!/usr/bin/ruby

# Generate Armstrong numbers.

# Armstrong (or pluperfect, or Plus Perfect, or narcissistic) numbers: m-digit positive numbers equal to sum of the m-th powers of their digits.
#   https://oeis.org/A005188

# See also:
#   https://rosettacode.org/wiki/Own_digits_power_sum

func armstrong_numbers(n, base=10) {

    var D = @(^base)
    var P = D.map {|d| d**n }

    var list = []

    D.combinations_with_repetition(n, {|*c|
        var v = c.sum {|d| P[d] }
        if (v.digits(base).sort == c) {
            list.push(v)
        }
    })

    list.sort
}

for n in (3..6) {
    say ("For n = #{'%2d' % n}: ", armstrong_numbers(n))
}

__END__
For n =  3: [153, 370, 371, 407]
For n =  4: [1634, 8208, 9474]
For n =  5: [54748, 92727, 93084]
For n =  6: [548834]
For n =  7: [1741725, 4210818, 9800817, 9926315]
For n =  8: [24678050, 24678051, 88593477]
For n =  9: [146511208, 472335975, 534494836, 912985153]
For n = 10: [4679307774]