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Search: id:A087155
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| A087155 |
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Primes which are palindromes in more than one base. |
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+0
1
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| 5, 7, 13, 17, 23, 29, 31, 37, 41, 43, 59, 61, 67, 71, 73, 83, 89, 97, 101, 107, 109, 113, 127, 131, 151, 157, 173, 181, 191, 193, 197, 199, 211, 227, 229, 233, 239, 241, 251, 257, 271, 277, 281, 307, 313, 331, 337, 349, 353, 373, 379, 383, 397, 401, 409, 419
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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17 is in the list because 17 base 2 = 10001, 17 base 4 = 101 and 17 base 16 = 11, three palindromes. 19 is not in the list because 19 is not a palindrome for any base other that base 18.
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PROGRAM
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(PARI) q=1; forprime(m=3, 500, count=0; for(b=2, m-1, w=b+1; k=0; i=m; while(i>0, k=k*w+i%b; i=floor(i/b)); l=0; j=k; while(j>0, l=l*w+j%w; j=floor(j/w)); if(l==k, count=count+1; if(count>1, print1(m, ", "); q=b; m=nextprime(m+1); q=1; b=1, q=b), )))
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CROSSREFS
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Sequence in context: A040125 A106067 A028311 this_sequence A045442 A095283 A163385
Adjacent sequences: A087152 A087153 A087154 this_sequence A087156 A087157 A087158
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KEYWORD
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base,nonn
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AUTHOR
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Randy L. Ekl (Randy.Ekl(AT)Motorola.com), Oct 18 2003
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