Jacobsthal numbers
my $jacobsthal = cache lazy 0, 1, * × 2 + * … *;
my $jacobsthal-lucas = lazy 2, 1, * × 2 + * … *;
say "First 30 Jacobsthal numbers:";
say $jacobsthal[^30].batch(5)».fmt("%9d").join: "\n";
say "\nFirst 30 Jacobsthal-Lucas numbers:";
say $jacobsthal-lucas[^30].batch(5)».fmt("%9d").join: "\n";
say "\nFirst 20 Jacobsthal oblong numbers:";
say (^∞).map( { $jacobsthal[$_] × $jacobsthal[$_+1] } )[^20].batch(5)».fmt("%11d").join: "\n";
say "\nFirst 20 Jacobsthal primes:";
say $jacobsthal.grep( &is-prime )[^20].join: "\n";
Output:
First 30 Jacobsthal numbers:
0 1 1 3 5
11 21 43 85 171
341 683 1365 2731 5461
10923 21845 43691 87381 174763
349525 699051 1398101 2796203 5592405
11184811 22369621 44739243 89478485 178956971
First 30 Jacobsthal-Lucas numbers:
2 1 5 7 17
31 65 127 257 511
1025 2047 4097 8191 16385
32767 65537 131071 262145 524287
1048577 2097151 4194305 8388607 16777217
33554431 67108865 134217727 268435457 536870911
First 20 Jacobsthal oblong numbers:
0 1 3 15 55
231 903 3655 14535 58311
232903 932295 3727815 14913991 59650503
238612935 954429895 3817763271 15270965703 61084037575
First 20 Jacobsthal primes:
3
5
11
43
683
2731
43691
174763
2796203
715827883
2932031007403
768614336404564651
201487636602438195784363
845100400152152934331135470251
56713727820156410577229101238628035243
62357403192785191176690552862561408838653121833643
1046183622564446793972631570534611069350392574077339085483
267823007376498379256993682056860433753700498963798805883563
5562466239377370006237035693149875298444543026970449921737087520370363869220418099018130434731
95562442332919646317117537304253622533190207882011713489066201641121786503686867002917439712921903606443
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