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A255161
Prime numbers with more than one 1 < k < 10 for which the base-k representation is palindromic.
1
2, 3, 5, 7, 17, 31, 67, 73, 107, 109, 127, 173, 191, 227, 257, 373, 701, 1667, 2293, 4289, 5189, 6761, 7517, 7703, 9103, 12547, 14891, 15083, 16319, 19433, 28807, 31727, 47653, 65537, 69313, 83269, 85093, 86293, 262657, 295433, 444713, 663571, 1053953, 1063613
OFFSET
1,1
LINKS
Chai Wah Wu, Table of n, a(n) for n = 1..3793 (all terms < 10^14).
EXAMPLE
17 belongs to the sequence as for more than one one-digit base (2 and 4) its base representation is palindromic (in base 2 the representation is 10001, in base 4 the representation is 101).
13 does not belong to the sequence since only in one one-digit base (namely, base 3) is its base representation (111) palindromic.
PROG
(PARI) ispal(n, b)=my(v=digits(n, b)); for(i=1, #v\2, if(v[i]!=v[#v+1-i], return(0))); 1
is(n)=sum(b=2, 9, ispal(n, b))>1 && isprime(n) \\ Charles R Greathouse IV, Feb 21 2015
CROSSREFS
Cf. A087155 (without restriction k<10).
Sequence in context: A074788 A262833 A070805 * A103385 A103389 A103387
KEYWORD
nonn,base
AUTHOR
Pierandrea Formusa, Feb 15 2015
STATUS
approved