A199305 Palindromic primes in the sense of A007500 with digits '0', '1' and '5' only.

5, 11, 101, 151, 1151, 1511, 10151, 10501, 11551, 15101, 15511, 15551, 100511, 110051, 115001, 150011, 150151, 151051, 1001551, 1051051, 1055501, 1115551, 1150151, 1150511, 1501501, 1510511, 1550551, 1551001, 1551551, 1555111, 10000511, 10011101, 10011511, 10055011, 10101551

Offset: 1

Author

M. F. Hasler, Nov 06 2011

Keywords

• nonn
• base

Comments

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.

Crossrefs

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

Programs

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

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