A199305 - OEIS

%I #16 Sep 08 2022 08:46:00

%S 5,11,101,151,1151,1511,10151,10501,11551,15101,15511,15551,100511,

%T 110051,115001,150011,150151,151051,1001551,1051051,1055501,1115551,

%U 1150151,1150511,1501501,1510511,1550551,1551001,1551551,1555111,10000511,10011101,10011511,10055011,10101551

%N Palindromic primes in the sense of A007500 with digits '0', '1' and '5' only.

%C All terms, except for the initial 5, start and end with the digit '1'. This fact could be used to significantly speed up the given program.

%o (PARI) a(n=50, list=0, L=[0, 1, 5], 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 [0,1,5] and IsPrime(Seqint(Reverse(Intseq(p))))]; // _Bruno Berselli_, Nov 07 2011

%Y Cf. A020449-A020472, A199325-A199329, A087510-A087515.

%K nonn,base

%O 1,1

%A _M. F. Hasler_, Nov 06 2011