Pairs with common factors: Difference between revisions

=={{header|Factor}}==

{{works with|Factor|0.99 2022-04-03}}

<lang factor>USING: formatting grouping io kernel math math.functions

math.primes.factors prettyprint ranges sequences

tools.memory.private ;

: totient-sum ( n -- sum )

[1..b] [ totient ] map-sum ;

: a ( n -- a(n) )

dup [ 1 - * 2 / ] keep totient-sum - ;

"Number of pairs with common factors - first 100 terms:" print

100 [1..b] [ a commas ] map 10 group simple-table. nl

7 <iota> [ dup 10^ a commas "Term #1e%d: %s\n" printf ] each</lang>

{{out}}

<pre>

Number of pairs with common factors - first 100 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

Term #1e0: 0

Term #1e1: 14

Term #1e2: 1,907

Term #1e3: 195,309

Term #1e4: 19,597,515

Term #1e5: 1,960,299,247

Term #1e6: 196,035,947,609

</pre>