A070156 - OEIS

%I #15 Jun 21 2024 06:38:41

%S 4,6,180,3390,18060,19380,34500,92220,92640,96180,114660,127680,

%T 133980,140760,159630,161880,172170,207480,254280,255840,263820,

%U 296910,309780,378570,380880,397590,408690,422880,432660,440550,511170,540390,572940

%N Numbers k such that k-1, k+1, k^2+1 and k^4+1 are all prime numbers.

%H Amiram Eldar, <a href="/A070156/b070156.txt">Table of n, a(n) for n = 1..10000</a>

%e For n = 6: 5, 7, 37, 1297 are all primes.

%t Do[s=n; If[PrimeQ[n-1]&&PrimeQ[n+1]&&PrimeQ[1+n^2] &&PrimeQ[1+n^4], Print[n]], {n, 1, 1000000}]

%o (PARI) is(k) = isprime(k-1) && isprime(k+1) && isprime(k^2+1) && isprime(k^4+1); \\ _Amiram Eldar_, Jun 21 2024

%Y Subsequence of A070155.

%Y Cf. A001359.

%K easy,nonn

%O 1,1

%A _Labos Elemer_, Apr 23 2002

%E Offset corrected by _Amiram Eldar_, Jun 21 2024