Twin primes: Difference between revisions
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> 1000
> 35 twin prime pairs.
</pre>
=={{header|Phix}}==
<lang Phix>function twin_primes(integer maxp)
integer n = 0, -- result
pn = 2 -- next prime index
p, -- a prime, <= maxp
prev_p = 2,
while true do
p = get_prime(pn)
if p>maxp then exit end if
n += (p = prevp+2)
prevp = p
pn += 1
end while
return n
end function
for p=1 to 9 do
integer p10 = power(10,p)
printf(1,"Twin prime pairs less than %,d: %,d\n",{p10,twin_primes(p10)})
end for</lang>
{{out}}
<pre>
Twin prime pairs less than 10: 2
Twin prime pairs less than 100: 8
Twin prime pairs less than 1,000: 35
Twin prime pairs less than 10,000: 205
Twin prime pairs less than 100,000: 1,224
Twin prime pairs less than 1,000,000: 8,169
Twin prime pairs less than 10,000,000: 58,980
Twin prime pairs less than 100,000,000: 440,312
Twin prime pairs less than 1,000,000,000: 3,424,506
</pre>
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