OFFSET
1,1
COMMENTS
This is the subsequence of primes in A018846. - M. F. Hasler, May 05 2012
LINKS
Chai Wah Wu, Table of n, a(n) for n = 1..10000 (terms 1..648 from M. F. Hasler)
MATHEMATICA
lst = {}; fQ[n_] := Block[{allset = {0, 1, 2, 5, 6, 8, 9}, id = IntegerDigits@n}, Union@ Join[id, allset] == allset && Reverse[id /. {6 -> 9, 9 -> 6}] == id]; Do[ If[ PrimeQ@n && fQ@n, AppendTo[lst, n]], {n, 700000}]; lst (* Robert G. Wilson v, Feb 27 2007 *)
PROG
(PARI) {write("/tmp/b018847.txt", "1 2\n2 5"); c=2; s2=[0, 1, 2, 5, 6, 8, 9]; s=[0, 1, 2, 5, 8]; s1=[0, 1, 2, 5, 9, 8, 6]; for(n=2, 9, p1=vector( (n+1)\2, i, 10^(i-1)); p2=vector( (n+1)\2, i, 10^(n-i)); forvec( v=vector((n+1)\2, i, if( i>1, [ 1, if( i>n\2, #s, #s1)], [2, 5])), v[1]==3 & v[1]=5; ispseudoprime( t=sum(i=1, n\2, p1[i]*s1[v[i]]+p2[i]*s2[v[i]] ) +if(n%2, p1[#p1]*s[v[#v]] )) & /* print1(t", ") */ write("/tmp/b018847.txt", c++" "t)))} \\ - M. F. Hasler, Apr 26 2012
(PARI) is_A018847(n, t=Vec("012..59.86"))={ isprime(n) & apply(x->t[eval(x)+1], n=Vec(Str(n)))==vecextract(n, "-1..1") } \\ - M. F. Hasler, May 05 2012
(Python)
from itertools import count, islice
from sympy import isprime
def A018847_gen(): # generator of terms
r, t, u = ''.maketrans('69', '96'), set('0125689'), {0, 1, 2, 5, 8}
for x in count(1):
for y in range(10**(x-1), 10**x):
if y%10 in u:
s = str(y)
if set(s) <= t and isprime(m:=int(s+s[-2::-1].translate(r))):
yield m
for y in range(10**(x-1), 10**x):
s = str(y)
if set(s) <= t and isprime(m:=int(s+s[::-1].translate(r))):
yield m
CROSSREFS
KEYWORD
nonn,base
AUTHOR
STATUS
approved