Pairs with common factors: Difference between revisions
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The 1,000,000th pair with common factors count is 196,035,947,609
</pre>
=={{header|Perl}}==
{{libheader|ntheory}}
<syntaxhighlight lang="perl" line>use v5.36;
use ntheory 'factor';
use List::Util qw<sum product uniq max>;
sub comma { reverse ((reverse shift) =~ s/(.{3})/$1,/gr) =~ s/^,//r }
sub table ($c, @V) { my $t = $c * (my $w = 2 + max map {length} @V); ( sprintf( ('%'.$w.'s')x@V, @V) ) =~ s/.{1,$t}\K/\n/gr }
my($max, @phi, @n_pairs) = (100, 0);
for my $t (1..$max) { push @phi, $t * product map { 1 - 1/$_ } uniq factor($t) }
push @n_pairs, comma $_ * ($_ - 1) / 2 + 1 - sum @phi[1..$_] for 1..$max;
say 'Number of pairs with common factors - first one hundred terms:';
say table 10, @n_pairs;
</syntaxhighlight>
{{out}}
<pre>Number of pairs with common factors - first one hundred terms:
0 0 0 1 1 4 4 7 9 14
14 21 21 28 34 41 41 52 52 63
71 82 82 97 101 114 122 137 137 158
158 173 185 202 212 235 235 254 268 291
291 320 320 343 363 386 386 417 423 452
470 497 497 532 546 577 597 626 626 669
669 700 726 757 773 818 818 853 877 922
922 969 969 1,006 1,040 1,079 1,095 1,148 1,148 1,195
1,221 1,262 1,262 1,321 1,341 1,384 1,414 1,461 1,461 1,526
1,544 1,591 1,623 1,670 1,692 1,755 1,755 1,810 1,848 1,907</pre>
=={{header|Phix}}==
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