Source code in the langur programming language

val .fermat = f 2 ^ 2 ^ .n + 1

val .factors = f(var .x) {
    for[.f=[]] .i, .s = 2, truncate .x ^/ 2; .i < .s; .i += 1 {
        if .x div .i {
            .f ~= [.i]
            .x \= .i
            .s = truncate .x ^/ 2
        }
    } ~ [.x]
}

writeln "first 10 Fermat numbers"
for .i in 0..9 {
    writeln $"F\(.i + 16x2080:cp) = \(.fermat(.i))"
}
writeln()

writeln "factors of first few Fermat numbers"
for .i in 0..9 {
    val .ferm = .fermat(.i)
    val .fac = .factors(.ferm)
    if len(.fac) == 1 {
        writeln $"F\(.i + 16x2080:cp) is prime"
    } else {
        writeln $"F\(.i + 16x2080:cp) factors: ", .fac
    }
}