Factorial primes: Difference between revisions

</pre>

=={{header|Kotlin}}==

Similar to Java implementation, but using Kotlin's String templates, overloaded BigInteger operators and an extension function to make the code easier to read:

<syntaxhighlight lang="kotlin">

import java.math.BigInteger

import java.math.BigInteger.ONE

enum class Difference(private val displayText: String) {

MINUS_ONE("- 1"), PLUS_ONE("+ 1");

override fun toString(): String {

return displayText

}

}

fun main() {

var currentFactorial = ONE

var highestFactor = 1L

var found = 0

while(found < 30) {

if ((currentFactorial - ONE).isProbablePrime(25)) {

printlnFactorialPrime(currentFactorial - ONE, highestFactor, Difference.MINUS_ONE)

found++

}

if ((currentFactorial + ONE).isProbablePrime(25)) {

printlnFactorialPrime(currentFactorial + ONE, highestFactor, Difference.PLUS_ONE)

found++

}

highestFactor++

currentFactorial *= BigInteger.valueOf(highestFactor)

}

}

fun printlnFactorialPrime(factorialPrime: BigInteger, base: Long, difference: Difference) =

println("${base}! $difference = ${factorialPrime.shortenIfNecessary()}")

fun BigInteger.shortenIfNecessary(): String {

val digits = toString()

val length = digits.length

return if (length <= 40) {

digits

} else {

"${digits.take(20)}...${digits.takeLast(20)} ($length digits)"

}

}

</syntaxhighlight>{{out}}

<pre>

1! + 1 = 2

2! + 1 = 3

3! - 1 = 5

3! + 1 = 7

4! - 1 = 23

6! - 1 = 719

7! - 1 = 5039

11! + 1 = 39916801

12! - 1 = 479001599

14! - 1 = 87178291199

27! + 1 = 10888869450418352160768000001

30! - 1 = 265252859812191058636308479999999

32! - 1 = 263130836933693530167218012159999999

33! - 1 = 8683317618811886495518194401279999999

37! + 1 = 13763753091226345046...79581580902400000001 (44 digits)

38! - 1 = 52302261746660111176...24100074291199999999 (45 digits)

41! + 1 = 33452526613163807108...40751665152000000001 (50 digits)

73! + 1 = 44701154615126843408...03680000000000000001 (106 digits)

77! + 1 = 14518309202828586963...48000000000000000001 (114 digits)

94! - 1 = 10873661566567430802...99999999999999999999 (147 digits)

116! + 1 = 33931086844518982011...00000000000000000001 (191 digits)

154! + 1 = 30897696138473508879...00000000000000000001 (272 digits)

166! - 1 = 90036917057784373664...99999999999999999999 (298 digits)

320! + 1 = 21161033472192524829...00000000000000000001 (665 digits)

324! - 1 = 22889974601791023211...99999999999999999999 (675 digits)

340! + 1 = 51008644721037110809...00000000000000000001 (715 digits)

379! - 1 = 24840307460964707050...99999999999999999999 (815 digits)

399! + 1 = 16008630711655973815...00000000000000000001 (867 digits)

427! + 1 = 29063471769607348411...00000000000000000001 (940 digits)

469! - 1 = 67718096668149510900...99999999999999999999 (1051 digits)