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- #!/usr/bin/perl
- # Daniel "Trizen" Șuteu
- # Date: 28 August 2022
- # https://github.com/trizen
- # Generate all the squarefree Fermat pseudoprimes to given a base with n prime factors in a given range [a,b]. (not in sorted order)
- # See also:
- # https://en.wikipedia.org/wiki/Almost_prime
- use 5.036;
- use ntheory qw(:all);
- use Math::GMPz;
- my $max_p = 1000000;
- my %znorder = map { $_ => znorder(2, $_) } @{primes($max_p)};
- sub fermat_pseudoprimes_in_range ($A, $B, $k, $base, $callback) {
- #my $m = "8833404609327838592895595408965";
- #my $m = "1614825036214963273306005";
- #my $m = Math::GMPz->new("19258022593463164626195195");
- #my $m = Math::GMPz->new("19976310800932286865"); # finds new abundant Fermat psp
- my $m = Math::GMPz->new("2799500171953451613547965"); # finds new abundant Fermat psp
- #my $m = Math::GMPz->new("551501533874829967868949105"); # finds new abundant Fermat psp
- #my $m = Math::GMPz->new("1389172629407632160878965"); # finds new abundant Fermat psp
- #my $m = Math::GMPz->new("3935333227783660512405"); # finds new abundant Fermat psp
- #my $m = Math::GMPz->new("15312580652854710165"); # finds new abundant Fermat psp
- #my $m = Math::GMPz->new("7051637712729097263345");
- #my $m = Math::GMPz->new("1256975577207099774483036285");
- #my $m = Math::GMPz->new("24383833295");
- my $L = znorder($base, $m);
- $L = Math::GMPz->new("$L");
- $A = $A*$m;
- $B = $B*$m;
- $A = vecmax($A, pn_primorial($k));
- $A = Math::GMPz->new("$A");
- $B = Math::GMPz->new("$B");
- if ($B > Math::GMPz->new("898943937249247967890084629421065")) {
- $B = Math::GMPz->new("898943937249247967890084629421065");
- }
- if ($A > $B) {
- return;
- }
- my $u = Math::GMPz::Rmpz_init();
- my $v = Math::GMPz::Rmpz_init();
- sub ($m, $L, $lo, $k) {
- Math::GMPz::Rmpz_tdiv_q($u, $B, $m);
- Math::GMPz::Rmpz_root($u, $u, $k);
- my $hi = Math::GMPz::Rmpz_get_ui($u);
- $hi = vecmin($max_p, $hi);
- if ($lo > $hi) {
- return;
- }
- if ($k == 1) {
- Math::GMPz::Rmpz_cdiv_q($u, $A, $m);
- if (Math::GMPz::Rmpz_fits_ulong_p($u)) {
- $lo = vecmax($lo, Math::GMPz::Rmpz_get_ui($u));
- }
- elsif (Math::GMPz::Rmpz_cmp_ui($u, $lo) > 0) {
- if (Math::GMPz::Rmpz_cmp_ui($u, $hi) > 0) {
- return;
- }
- $lo = Math::GMPz::Rmpz_get_ui($u);
- }
- if ($lo > $hi) {
- return;
- }
- Math::GMPz::Rmpz_invert($v, $m, $L) || return;
- if (Math::GMPz::Rmpz_cmp_ui($v, $hi) > 0) {
- return;
- }
- if (Math::GMPz::Rmpz_fits_ulong_p($L)) {
- $L = Math::GMPz::Rmpz_get_ui($L);
- }
- my $t = Math::GMPz::Rmpz_get_ui($v);
- $t > $hi && return;
- $t += $L while ($t < $lo);
- for (my $p = $t ; $p <= $hi ; $p += $L) {
- if (is_prime($p) and $base % $p != 0 and !Math::GMPz::Rmpz_divisible_ui_p($m, $p)) {
- Math::GMPz::Rmpz_mul_ui($v, $m, $p);
- Math::GMPz::Rmpz_sub_ui($u, $v, 1);
- my $z = ($znorder{$p} // znorder($base, $p));
- if (Math::GMPz::Rmpz_divisible_ui_p($u, $z)) {
- $callback->(Math::GMPz::Rmpz_init_set($v));
- }
- }
- }
- return;
- }
- my $t = Math::GMPz::Rmpz_init();
- my $lcm = Math::GMPz::Rmpz_init();
- foreach my $p (@{primes($lo, $hi)}) {
- Math::GMPz::Rmpz_divisible_ui_p($m, $p) and next;
- $base % $p == 0 and next;
- my $z = ($znorder{$p} // znorder($base, $p));
- Math::GMPz::Rmpz_gcd_ui($Math::GMPz::NULL, $m, $z) == 1 or next;
- Math::GMPz::Rmpz_lcm_ui($lcm, $L, $z);
- Math::GMPz::Rmpz_mul_ui($t, $m, $p);
- __SUB__->($t, $lcm, $p + 1, $k - 1);
- }
- }
- ->($m, $L, 3, $k);
- return 1;
- }
- my $base = 2;
- my $from = Math::GMPz->new("2");
- my $upto = 2*$from;
- while (1) {
- my $ok = 0;
- say "# Range: ($from, $upto)";
- foreach my $k (2..100) {
- fermat_pseudoprimes_in_range($from, $upto, $k, $base, sub ($n) { say $n }) or next;
- $ok = 1;
- }
- $ok || last;
- $from = $upto+1;
- $upto = 2*$from;
- }
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