Sequence: nth number with exactly n divisors
Sequence: nth number with exactly n divisors is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.
Calculate the sequence where each term an is the nth that has n divisors.
- Task
Show here, on this page, at least the first 10 terms of the sequence.
- See also
- Related tasks
Perl 6
<lang perl6>sub div-count (\x) {
return 2 if x.is-prime; +flat (1 .. x.sqrt.floor).map: -> \d { unless x % d { my \y = x div d; y == d ?? y !! (y, d) } }
}
my $limit = 15;
my @primes = grep { .is-prime }, 1..*; @primes[$limit]; # prime the array. SCNR
put "\nFirst 15 terms of OEIS:A073916"; put (1..$limit).hyper(:2batch).map: -> $n {
($n > 4 and $n.is-prime) ?? exp($n - 1, @primes[$n - 1]) !! do { my $i = 0; my $iterator = $n %% 2 ?? (1..*) !! (1..*).map: *²; $iterator.first: { next unless $n == .&div-count; next unless ++$i == $n; $_ } }
};</lang>
First 15 terms of OEIS:A073916 1 3 25 14 14641 44 24137569 70 1089 405 819628286980801 160 22563490300366186081 2752 9801