prog.sf

#!/usr/bin/ruby

# The number of terms of A354558 that are <= 10^n.
# https://oeis.org/A354559

# Known terms:
#   1, 2, 5, 13, 28, 79, 204, 549, 1509, 4231, 12072, 36426, 112589

func a(n) {

    var k = 10**n
    #var smooth = []
    var count = 0
    var primes = []

    k.isqrt.each_prime {|p|
        var pp = p*p
        primes << p
        #smooth << smooth_numbers(idiv(k, pp), p.primes).map{_ * pp}...
        count += smooth_numbers(idiv(k, pp), primes).map{_ * pp}.count { .inc.gpf.sqr `divides` .inc }
    }

    #smooth.grep{.inc.gpf.sqr `divides` .inc}
    #smooth.count{.inc.gpf.sqr `divides` .inc}
    return count
}

for n in (1..15) {
    say "a(#{n}) = #{a(n)}"
}

__END__

a(1) = 1
a(2) = 2
a(3) = 5
a(4) = 13
a(5) = 28
a(6) = 79
a(7) = 204
a(8) = 549
a(9) = 1509
a(10) = 4231