A101792 - OEIS

%I #15 May 13 2024 02:15:02

%S 23,359,719,1439,2039,2063,2903,3023,3623,3863,4919,5399,5639,6983,

%T 7079,7823,10799,12263,14159,14303,21383,22343,22943,24239,25799,

%U 25919,33623,34319,36383,38639,39983,40823,42023,42359,44543,46199,47639,48479,49103,54959

%N Primes of the form 8*k-1 such that 4*k-1 and 16*k-1 are also primes.

%H Amiram Eldar, <a href="/A101792/b101792.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = 8*A101790(n) - 1 = 2*A101791(n) + 1. - _Amiram Eldar_, May 13 2024

%e 4*3 - 1 = 11, 8*3 - 1 = 23 and 16*3 - 1 = 47 are primes, so 23 is a term.

%t 8 * Select[Range[10^4], And @@ PrimeQ[2^Range[2, 4]*# - 1] &] - 1 (* _Amiram Eldar_, May 13 2024 *)

%o (PARI) for(k=1,7000,if(isprime(8*k-1)&&isprime(4*k-1)&&isprime(16*k-1),print1(8*k-1,", "))) \\ _Hugo Pfoertner_, Sep 07 2021

%Y Cf. A002515, A101790, A101791, A101793.

%Y Subsequence of A007522.

%Y Subsequences: A101796, A101996.

%K easy,nonn

%O 1,1

%A Douglas Stones (dssto1(AT)student.monash.edu.au), Dec 16 2004