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+#!/usr/bin/env python3
+
+# Challenge 147
+#
+# TASK #1 > Truncatable Prime
+# Submitted by: Mohammad S Anwar
+# Write a script to generate first 20 left-truncatable prime numbers in base 10.
+#
+# In number theory, a left-truncatable prime is a prime number which, in a given
+# base, contains no 0, and if the leading left digit is successively removed,
+# then all resulting numbers are primes.
+#
+# Example
+# 9137 is one such left-truncatable prime since 9137, 137, 37 and 7 are all
+# prime numbers.
+
+from sympy import isprime, nextprime
+
+def left_truncatable_prime_it():
+    prime = None
+    while True:
+        prime = nextprime(prime) if prime is not None else 2
+        if is_left_truncatable_prime(prime):
+            yield prime
+
+def is_left_truncatable_prime(p):
+    while True:
+        if not isprime(p):
+            return False
+        p = int(str(p)[1:]) if len(str(p)) > 1 else ''
+        if p == '':
+            return True
+
+it = left_truncatable_prime_it()
+out = [next(it) for _ in range(20)]
+print(", ".join(map(str, out)))