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A199304 Palindromic primes in the sense of A007500 with digits '0', '1' and '4' only. 1

%I #20 Sep 08 2022 08:46:00

%S 11,101,11411,100411,101141,114001,114041,140411,141101,1004141,

%T 1010411,1040141,1041041,1100441,1114111,1140101,1144441,1401401,

%U 1410401,1411141,1414001,1440011,1444411,1444441,10010411,10011101,10041011,10044011

%N Palindromic primes in the sense of A007500 with digits '0', '1' and '4' only.

%C All terms start and end with the digit 1.

%H Robert Israel, <a href="/A199304/b199304.txt">Table of n, a(n) for n = 1..10000</a>

%p F:= proc(d) local A0, A4, Res, q, r;

%p Res:= NULL;

%p q:= (10^(d+1)-1)/9;

%p for A0 in combinat:-powerset({$1..d-1}) do

%p for A4 in combinat:-powerset({$1..d-1} minus A0) do

%p r:= q - add(10^i,i=A0) + 3*add(10^i,i=A4);

%p if isprime(r) and isprime(q - add(10^(d-i),i=A0) + 3*add(10^(d-i),i=A4)) then

%p Res:= Res, r

%p fi

%p od od;

%p Res

%p end proc:

%p sort([seq(F(d),d=1..7)]); # _Robert Israel_, May 03 2018

%o (PARI) allow=Vec("014");forprime(p=1,default(primelimit),setminus( Set( Vec(Str( p ))),allow)&next;isprime(A004086(p))&print1(p",")) /* better use the more efficient code below */

%o (PARI) a(n=50,list=0,L=[0,1,4],needpal=1)={ for(d=1,1e9, u=vector(d,i,10^(d-i))~; forvec(v=vector(d,i,[1+(i==1&!L[1]),#L]), isprime(t=vector(d,i,L[v[i]])*u) || next; needpal & !isprime(A004086(t)) & next; list & print1(t","); n-- || return(t)))} \\ _M. F. Hasler_, Nov 06 2011

%o (Magma) [p: p in PrimesUpTo(10^8) | Set(Intseq(p)) subset [0,1,4] and IsPrime(Seqint(Reverse(Intseq(p))))]; // _Bruno Berselli_, Nov 07 2011

%Y Cf. A020449 - A020472, A199325 - A199329, A199302 - A199306.

%K nonn,base

%O 1,1

%A _M. F. Hasler_, Nov 04 2011

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Last modified March 29 06:44 EDT 2024. Contains 371265 sequences. (Running on oeis4.)