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- #!/usr/bin/perl
- # a(n) is the smallest number with exactly n divisors that are n-gonal numbers.
- # https://oeis.org/A358539
- # Known terms:
- # 6, 36, 210, 1260, 6426, 3360, 351000, 207900, 3749460, 1153152, 15036840
- use 5.020;
- use ntheory qw(:all);
- use experimental qw(signatures);
- sub a($n) {
- my $count;
- for(my $k = 2; ; ++$k) {
- $count = 0;
- foreach my $d (divisors($k)) {
- if (is_polygonal($d, $n)) {
- ++$count;
- }
- }
- if ($count == $n) {
- return $k;
- }
- }
- }
- foreach my $n (3..100) {
- say "a($n) = ", a($n);
- }
- __END__
- a(3) = 6
- a(4) = 36
- a(5) = 210
- a(6) = 1260
- a(7) = 6426
- a(8) = 3360
- a(9) = 351000
- a(10) = 207900
- a(11) = 3749460
- a(12) = 1153152
- a(13) = 15036840
- a(14) = 204204000
- a(15) = 213825150
- a(16) = 11737440
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