Data commit

Task/Strong-and-weak-primes/Python/strong-and-weak-primes.py

@@ -0,0 +1,37 @@
+import numpy as np
+
+def primesfrom2to(n):
+    # https://stackoverflow.com/questions/2068372/fastest-way-to-list-all-primes-below-n-in-python/3035188#3035188
+    """ Input n>=6, Returns a array of primes, 2 <= p < n """
+    sieve = np.ones(n//3 + (n%6==2), dtype=np.bool)
+    sieve[0] = False
+    for i in range(int(n**0.5)//3+1):
+        if sieve[i]:
+            k=3*i+1|1
+            sieve[      ((k*k)//3)      ::2*k] = False
+            sieve[(k*k+4*k-2*k*(i&1))//3::2*k] = False
+    return np.r_[2,3,((3*np.nonzero(sieve)[0]+1)|1)]
+
+p = primes10m   = primesfrom2to(10_000_000)
+s = strong10m   = [t for s, t, u in zip(p, p[1:], p[2:])
+                   if t > (s + u) / 2]
+w = weak10m     = [t for s, t, u in zip(p, p[1:], p[2:])
+                   if t < (s + u) / 2]
+b = balanced10m = [t for s, t, u in zip(p, p[1:], p[2:])
+                   if t == (s + u) / 2]
+
+print('The first   36   strong primes:', s[:36])
+print('The   count   of the strong primes below   1,000,000:',
+      sum(1 for p in s if p < 1_000_000))
+print('The   count   of the strong primes below  10,000,000:', len(s))
+print('\nThe first   37   weak primes:', w[:37])
+print('The   count   of the weak   primes below   1,000,000:',
+      sum(1 for p in w if p < 1_000_000))
+print('The   count   of the weak   primes below  10,000,000:', len(w))
+print('\n\nThe first   10 balanced primes:', b[:10])
+print('The   count   of balanced   primes below   1,000,000:',
+      sum(1 for p in b if p < 1_000_000))
+print('The   count   of balanced   primes below  10,000,000:', len(b))
+print('\nTOTAL primes below   1,000,000:',
+      sum(1 for pr in p if pr < 1_000_000))
+print('TOTAL primes below  10,000,000:', len(p))