Ramanujan primes/twins: Difference between revisions
julia example
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Took 699.967994ms
</pre>
=={{header|Julia}}==
<lang julia>using Primes
function rajpairs(N, verbose, interval = 2)
maxpossramanujan(n) = Int(ceil(4n * log(4n) / log(2)))
prm = primes(maxpossramanujan(N))
pivec = accumulate(+, primesmask(maxpossramanujan(N)))
halfrpc = [pivec[p] - pivec[p ÷ 2] for p in prm]
lastrpc = last(halfrpc) + 1
for i in length(halfrpc):-1:1
if halfrpc[i] < lastrpc
lastrpc = halfrpc[i]
else
halfrpc[i] = 0
end
end
rajvec = [prm[i] for i in eachindex(prm) if halfrpc[i] > 0]
nrajtwins = count(rajvec[i] + interval == rajvec[i + 1] for i in 1:N-1)
verbose && println("There are $nrajtwins twins in the first $N Ramanujan primes.")
return nrajtwins
end
rajpairs(100000, false)
@time rajpairs(1000000, true)
</lang>{{out}}
<pre>
There are 74973 twins in the first 1000000 Ramanujan primes.
0.759511 seconds (50 allocations: 839.383 MiB, 5.64% gc time)
</pre>
=={{header|Phix}}==
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