Ormiston pairs
Ormiston pairs is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.
An Ormiston pair is two consecutive prime numbers which are anagrams, i.e. contain the same decimal digits but in a different order.
(1913, 1931) is the first such pair.
- Task
- Find and show the first 30 Ormiston pairs.
- Find and show the count of Ormiston pairs up to one million.
- Stretch
- Find and show the count of Ormiston pairs up to ten million.
- See also
Raku
use Lingua::EN::Numbers;
use List::Divvy;
my @primes = lazy (^∞).hyper.grep: &is-prime;
my @Ormistons = @primes.kv.map: { ($^value, @primes[$^key+1]) if $^value.comb.Bag eqv @primes[$^key+1].comb.Bag };
say @Ormistons[^30].batch(3)».map( { "({.[0].fmt: "%5d"}, {.[1].fmt: "%5d"})" } ).join: "\n";
say '';
say +@Ormistons.&before( *[1] > $_ ) ~ " Ormiston pairs before " ~ .Int.&cardinal for 1e5, 1e6, 1e7;
- Output:
( 1913, 1931) (18379, 18397) (19013, 19031) (25013, 25031) (34613, 34631) (35617, 35671) (35879, 35897) (36979, 36997) (37379, 37397) (37813, 37831) (40013, 40031) (40213, 40231) (40639, 40693) (45613, 45631) (48091, 48109) (49279, 49297) (51613, 51631) (55313, 55331) (56179, 56197) (56713, 56731) (58613, 58631) (63079, 63097) (63179, 63197) (64091, 64109) (65479, 65497) (66413, 66431) (74779, 74797) (75913, 75931) (76213, 76231) (76579, 76597) 40 Ormiston pairs before one hundred thousand 382 Ormiston pairs before one million 3722 Ormiston pairs before ten million