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A185267
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Smallest palindrome beginning with n-th prime.
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1
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2, 3, 5, 7, 11, 131, 171, 191, 232, 292, 313, 373, 414, 434, 474, 535, 595, 616, 676, 717, 737, 797, 838, 898, 979, 101, 10301, 10701, 10901, 11311, 12721, 131, 13731, 13931, 14941, 151, 15751, 16361, 16761, 17371, 17971, 181, 191, 19391, 19791, 1991, 2112, 22322
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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COMMENTS
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a(n) is itself prime for n = 1, 2, 3, 4, 5, 6, 8, 11, 12, 22, 26, 27, 30, 31, 32, 34, ... where a(n) = 2, 3, 5, 7, 11, 131, 191, 313, 373, 797, 101, 10301, 11311, 12721, 131, 13931, which are also in A002385. Although 979 begins with the prime p(25) = 97, and is a palindrome, it is not in the commented subsequence because 979 = 11 * 89 is semiprime rather than prime.
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LINKS
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FORMULA
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EXAMPLE
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a(6) = 131 because that is the smallest palindrome beginning (base 10) with p(6) = 13.
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PROG
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(Python)
from sympy import prime
p = prime(n)
s = str(p)
if s == s[::-1]:
return p
for i in range(1, len(s)):
if s[i:] == s[-1:i-1:-1]:
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CROSSREFS
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KEYWORD
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nonn,base,easy
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AUTHOR
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STATUS
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approved
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