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Search: id:A137779
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| A137779 |
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Number of bases (numbering systems, including unary) in which the nth prime is a palindrome having at least two digits. |
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+0
2
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| 1, 2, 3, 3, 2, 3, 4, 2, 3, 3, 4, 3, 3, 3, 2, 2, 3, 3, 4, 3, 4, 2, 3, 3, 3, 3, 2, 4, 4, 3, 4, 3, 2, 2, 2, 4, 4, 2, 2, 4, 2, 4, 5, 3, 4, 3, 4, 2, 4, 3, 3, 3, 4, 3, 6, 2, 2, 4, 4, 3, 2, 2, 4, 2, 5, 2, 3, 5, 2, 3, 5, 2, 2, 6, 5, 3, 2, 3, 4, 4, 4, 5, 3, 4, 2, 5, 3, 4, 4, 4, 3, 3, 4, 2, 3, 3, 3, 4, 4
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Each prime p > 2 is palindrome in at least base 1 and base p-1, since p = 1*(p-1)^1 + 1*(p-1)^0 and p = 1*1^(p-1) + 1*1(p-2) + ... + 1*1^1 + 1*1^0.
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LINKS
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Attila Olah, Table of n, a(n) for n = 1..10000
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EXAMPLE
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a(621) = 9 because the 621th prime (4591) is a palindrome in 9 bases: base 1, 19, 20, 24, 33, 37, 51, 54 and 4590 (4591 = 1*4590^1 + 1*4590^0).
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CROSSREFS
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Cf. A087911.
Sequence in context: A007538 A025076 A110006 this_sequence A107918 A002963 A046677
Adjacent sequences: A137776 A137777 A137778 this_sequence A137780 A137781 A137782
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KEYWORD
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easy,base,nonn
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AUTHOR
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Attila Olah (jolafix(AT)gmail.com), May 06 2008, corrected May 08 2008
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