

A088092


Palindromic primes p such that if each digit d is replaced by 10d then the resulting palindrome is also a prime.


1



3, 5, 7, 181, 191, 313, 353, 383, 727, 757, 797, 919, 929, 12421, 12721, 14341, 17971, 32323, 78787, 93139, 96769, 98389, 98689, 1129211, 1145411, 1153511, 1175711, 1178711, 1183811, 1221221, 1273721, 1328231, 1486841, 1633361, 1824281
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OFFSET

1,1


COMMENTS

Digit 0 is not allowed.  Robert Israel, Sep 14 2020


LINKS

Robert Israel, Table of n, a(n) for n = 1..10000


EXAMPLE

181 is a member as replacing 1 by 101 = 9 and 8 by 108 =2 gives 929 which is also a prime.


MAPLE

R:= NULL: count:= 0:
for d from 1 by 2 while count < 100 do
m:= ceil(d/2);
for r from 0 to 9^m1 do
L:= convert(9^m+r, base, 9)[1..m] + [1$m];
L:= [ seq(L[i], i=1..m1), op(L)];
x:= add(L[i]*10^(i1), i=1..d);
if isprime(x) and isprime((10^d1)*10/9x) then R:= R, x; count:= count+1
fi
od od:
R; # Robert Israel, Sep 14 2020


CROSSREFS

Cf. A002385 (palindromic primes).
Sequence in context: A128344 A259385 A114366 * A174271 A211678 A082756
Adjacent sequences: A088089 A088090 A088091 * A088093 A088094 A088095


KEYWORD

base,nonn


AUTHOR

Amarnath Murthy, Sep 23 2003


EXTENSIONS

Corrected and extended by David Wasserman, Jul 18 2005


STATUS

approved



