First of all if p and q are primes then p - q is even unless p=2 or q=2.
Next, there is no need to declare variable in Python.
Finally, there are optimized methods to access primes. Look
for prime_range, next_prime, Primes, etc
x = 3
while True:
y = (10**18 // x).next_prime()
ymax = (10**36 + x - 2) // x
while y <= ymax:
print("x = %d and y = %d" % (x, y))
y = y.next_prime()
x = x.next_prime()
Le 08/05/2020 à 23:00, u220e a écrit :
Hi. I'm trying to generate a list of pairs of primes (x,y) within a range
of values such that the digit length of their products is between 19 and
35. I've written a few different code variations that (unfortunately)
either (1) generate ALL the integer pairs (that equal 19, 20, 21, etc.) or
(2) never seem to halt.
I really want the iteration to be as follows: find the first pair that
equals 19, then locate the first pair that equals 20, and so on so until I
have one list of 17 pairs of primes---one pair for each digit length.
Here's what I have so far:
x=var('x')
y=var('y')
for x in sxrange (10**9,10**(36)):
for y in sxrange (961748941,982451653):
if x.is_prime()==1 and y.is_prime()==1:
if (floor(log((x*y),10)+1)<=35)==1:
print(x,y); print(floor(log((x*y),10)+1); break
Then I tried defining y=982451653 so I could use only one iterable using
the following code:
for x in sxrange (10**9,10**(36)):
if x.is_prime()==1:
if (floor(log((x*y),10)+1)>=19)==1:
continue
print(x,y); print(floor(log((x*y),10)+1); break
which returns only one value:
1000000007 982451653
18
Sorry for the n00b post. I've only been using Sage for three days.
Thanks,
David
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