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A023281 Primes that remain prime through 3 iterations of function f(x) = 4x + 3.

%I A023281 #24 Sep 08 2022 08:44:47
%S A023281 2,109,179,571,677,977,1279,1447,1747,1901,2207,2671,3119,3917,5011,
%T A023281 5399,5441,5569,5791,6211,6607,7079,7417,8369,8831,9221,9697,9769,
%U A023281 11821,11897,12347,13537,13669,13691,13729,13781,13907,14747,14851,15581,17231,17497
%N A023281 Primes that remain prime through 3 iterations of function f(x) = 4x + 3.
%C A023281 Primes p such that 4*p+3, 16*p+15 and 64*p+63 are also primes. - _Vincenzo Librandi_, Aug 04 2010
%H A023281 John Cerkan, <a href="/A023281/b023281.txt">Table of n, a(n) for n = 1..10000</a>
%p A023281 f:=proc(x) options operator, arrow: 4*x+3 end proc: a:=proc(n) if isprime(n)= true and isprime(f(n))=true and isprime(f(f(n)))=true and isprime(f(f(f(n)))) =true then n else end if end proc: seq(a(n),n=1..20000); # _Emeric Deutsch_, Jan 01 2008
%t A023281 Select[Prime@ Range@ 2100, Times @@ Boole@ PrimeQ@ Rest@ NestList[4 # + 3 &, #, 3] > 0 &] (* _Michael De Vlieger_, Sep 19 2016 *)
%o A023281 (Magma) [n: n in [1..150000] | IsPrime(n) and IsPrime(4*n+3) and IsPrime(16*n+15) and IsPrime(64*n+63)] // _Vincenzo Librandi_, Aug 04 2010
%o A023281 (PARI) is(n)=isprime(n) && isprime(4*n+3) && isprime(16*n+15) && isprime(64*n+63) \\ _Charles R Greathouse IV_, Sep 20 2016
%Y A023281 Subsequence of A023213, A023250, and of A095278.
%K A023281 nonn
%O A023281 1,1
%A A023281 _David W. Wilson_