Factorial primes
sub postfix:<!> ($n) { constant @F = (1, 1, |[\*] 2..*); @F[$n] }
sub abr ($_) { .chars < 41 ?? $_ !! .substr(0,20) ~ '..' ~ .substr(*-20) ~ " ({.chars} digits)" }
my $limit;
for 1..* {
my \f = .!;
++$limit and printf "%2d: %3d! - 1 = %s\n", $limit, $_, abr f -1 if (f -1).is-prime;
++$limit and printf "%2d: %3d! + 1 = %s\n", $limit, $_, abr f +1 if (f +1).is-prime;
exit if $limit >= 30
}
Output:
1: 1! + 1 = 2
2: 2! + 1 = 3
3: 3! - 1 = 5
4: 3! + 1 = 7
5: 4! - 1 = 23
6: 6! - 1 = 719
7: 7! - 1 = 5039
8: 11! + 1 = 39916801
9: 12! - 1 = 479001599
10: 14! - 1 = 87178291199
11: 27! + 1 = 10888869450418352160768000001
12: 30! - 1 = 265252859812191058636308479999999
13: 32! - 1 = 263130836933693530167218012159999999
14: 33! - 1 = 8683317618811886495518194401279999999
15: 37! + 1 = 13763753091226345046..79581580902400000001 (44 digits)
16: 38! - 1 = 52302261746660111176..24100074291199999999 (45 digits)
17: 41! + 1 = 33452526613163807108..40751665152000000001 (50 digits)
18: 73! + 1 = 44701154615126843408..03680000000000000001 (106 digits)
19: 77! + 1 = 14518309202828586963..48000000000000000001 (114 digits)
20: 94! - 1 = 10873661566567430802..99999999999999999999 (147 digits)
21: 116! + 1 = 33931086844518982011..00000000000000000001 (191 digits)
22: 154! + 1 = 30897696138473508879..00000000000000000001 (272 digits)
23: 166! - 1 = 90036917057784373664..99999999999999999999 (298 digits)
24: 320! + 1 = 21161033472192524829..00000000000000000001 (665 digits)
25: 324! - 1 = 22889974601791023211..99999999999999999999 (675 digits)
26: 340! + 1 = 51008644721037110809..00000000000000000001 (715 digits)
27: 379! - 1 = 24840307460964707050..99999999999999999999 (815 digits)
28: 399! + 1 = 16008630711655973815..00000000000000000001 (867 digits)
29: 427! + 1 = 29063471769607348411..00000000000000000001 (940 digits)
30: 469! - 1 = 67718096668149510900..99999999999999999999 (1051 digits)
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