Initial data commit

Task/Duffinian-numbers/Factor/duffinian-numbers.factor

@@ -0,0 +1,18 @@
+USING: combinators.short-circuit.smart grouping io kernel lists
+lists.lazy math math.primes math.primes.factors math.statistics
+prettyprint sequences sequences.deep ;
+
+: duffinian? ( n -- ? )
+    { [ prime? not ] [ dup divisors sum simple-gcd 1 = ] } && ;
+
+: duffinians ( -- list ) 3 lfrom [ duffinian? ] lfilter ;
+
+: triples ( -- list )
+    duffinians dup cdr dup cdr lzip lzip [ flatten ] lmap-lazy
+    [ differences { 1 1 } = ] lfilter ;
+
+"First 50 Duffinian numbers:" print
+50 duffinians ltake list>array 10 group simple-table. nl
+
+"First 15 Duffinian triplets:" print
+15 triples ltake list>array simple-table.