Special neighbor primes: Difference between revisions

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=={{header|Sidef}}==

<lang ruby>func special_neighbor_primes(upto) {

var list = []

upto.primes.each_cons(2, {|p1,p2|

var n = (p1 + p2 - 1)

if (n.is_prime) {

list << [p1, p2, n]

}

})

return list

}

with (100) {|n|

var list = special_neighbor_primes(n)

say "Found #{list.len} special neighbour primes < n:"

list.each_2d {|p1,p2,q|

printf(" (%2s, %2s) => %s\n", p1, p2, q)

}

}

say ''

for n in (1..7) {

var list = special_neighbor_primes(10**n)

say "Found #{list.len} special neighbour primes < 10^#{n}"

}</lang>

{{out}}

<pre>

Found 13 special neighbour primes < n:

( 3, 5) => 7

( 5, 7) => 11

( 7, 11) => 17

(11, 13) => 23

(13, 17) => 29

(19, 23) => 41

(29, 31) => 59

(31, 37) => 67

(41, 43) => 83

(43, 47) => 89

(61, 67) => 127

(67, 71) => 137

(73, 79) => 151

Found 2 special neighbour primes < 10^1

Found 13 special neighbour primes < 10^2

Found 71 special neighbour primes < 10^3

Found 367 special neighbour primes < 10^4

Found 2165 special neighbour primes < 10^5

Found 14526 special neighbour primes < 10^6

Found 103611 special neighbour primes < 10^7