algorithm - Generate a list of primes up to a certain number -

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i'm trying generate list of primes below 1 billion. i'm trying this, kind of structure pretty shitty. suggestions?

a <- 1:1000000000 d <- 0 b <- (i in a) {for (j in 1:i) {if (i %% j !=0) {d <- c(d,i)}}}

this implementation of sieve of eratosthenes algorithm in r.

sieve <- function(n) {    n <- as.integer(n)    if(n > 1e6) stop("n large")    primes <- rep(true, n)    primes[1] <- false    last.prime <- 2l    for(i in last.prime:floor(sqrt(n)))    {       primes[seq.int(2l*last.prime, n, last.prime)] <- false       last.prime <- last.prime + min(which(primes[(last.prime+1):n]))    }    which(primes) }   sieve(1000000)

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