A274381 Safe primes p such that p + 24 is also a safe prime.
23, 59, 83, 359, 479, 563, 839, 863, 1283, 2039, 2879, 2999, 3779, 4259, 4679, 5483, 7703, 10079, 12203, 13103, 23603, 26903, 27803, 30323, 31583, 33623, 35339, 41519, 43403, 44519, 44939, 53759, 55079, 57119, 57899, 58043, 65123, 66359, 70139, 70199, 76379, 77723, 79943
Offset: 1
Keywords
Examples
83 is a safe prime and so is 83 + 24 = 107. 4679 is a safe prime and so is 4679 + 24 = 4703.
Links
- John Cerkan, Table of n, a(n) for n = 1..10000
Programs
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Maple
A274381:=n->`if`(type((n-1)/2, prime) and isprime(n+24) and isprime(n) and type((n+23)/2, prime), n, NULL): seq(A274381(n), n=1..10^5); # Wesley Ivan Hurt, Jun 25 2016
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Mathematica
Select[Prime@ Range[10^4], PrimeQ[(# - 1)/2] && PrimeQ[# + 24] && PrimeQ[(23 + #)/2] &] (* Giovanni Resta, Jun 23 2016 *) Select[Prime[Range[8000]],AllTrue[{(#-1)/2,(#+23)/2,#+24},PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Dec 31 2019 *)
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PARI
lista(nn) = forprime(p=3, nn, if (isprime((p-1)/2) && isprime(q=p+24) && isprime((q-1)/2), print1(p, ", "))); \\ Michel Marcus, Jun 23 2016
Formula
{ x | both x and x + 24 are safe primes }.