Initial data commit

Task/Factorial-primes/Python/factorial-primes.py

@@ -0,0 +1,35 @@
+from itertools import count
+from itertools import islice
+from typing import Iterable
+from typing import Tuple
+
+import gmpy2
+
+
+def factorials() -> Iterable[int]:
+    fact = 1
+    for i in count(1):
+        yield fact
+        fact *= i
+
+
+def factorial_primes() -> Iterable[Tuple[int, int, str]]:
+    for n, fact in enumerate(factorials()):
+        if gmpy2.is_prime(fact - 1):
+            yield (n, fact - 1, "-")
+        if gmpy2.is_prime(fact + 1):
+            yield (n, fact + 1, "+")
+
+
+def print_factorial_primes(limit=10) -> None:
+    print(f"First {limit} factorial primes.")
+    for n, fact_prime, op in islice(factorial_primes(), 1, limit + 1):
+        s = str(fact_prime)
+        if len(s) > 40:
+            s = f"{s[:20]}...{s[-20:]} ({len(s)} digits)"
+        print(f"{n}! {op} 1 = {s}")
+
+
+if __name__ == "__main__":
+    import sys
+    print_factorial_primes(int(sys.argv[1]) if len(sys.argv) > 1 else 10)