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Search: id:A087911
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| A087911 |
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Smallest prime p that is a palindrome in n different bases < p. |
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+0
2
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| 2, 3, 5, 17, 191, 257, 1009, 4561, 4591, 21601, 57601, 54121, 86677, 176401, 415801, 291721, 950041, 1259701, 3049201, 1670761, 6098401, 3880801, 5654881, 13759201, 18618601, 14414401, 18960481, 15135121, 31600801, 45405361, 35814241
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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a(n) = A000040(A137779^(-1)(n)). - Attila Olah (jolafix(AT)gmail.com), May 06 2008, corrected May 08 2008
The sequence is not monotonic: a(10) > a(11) = 54121. - Attila Olah (jolafix(AT)gmail.com), May 06 2008, corrected May 08 2008
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LINKS
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Karl Hovekamp (karl.hovekamp(AT)web.de), Jan 01 2007, Table of n, a(n) for n = 1..55
Author?, Palindromic numbers
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EXAMPLE
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a(4) = 191 because 191 base 6 = 515, 191 base 9 = 232, 191 base 10 = 191, and 191 base 190 = 11, all palindromes. No numbers less than 191 can be representedin 4 such ways.
a(12) = 54121 because 54121 is a palindrome in 12 different bases, including base 1 and base 54120.
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PROGRAM
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(PARI) q=1; forprime(m=3, 20000, 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>q, print1(m, ", "); q=count, )))
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CROSSREFS
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Cf. A137779.
Adjacent sequences: A087908 A087909 A087910 this_sequence A087912 A087913 A087914
Sequence in context: A065952 A089983 A072858 this_sequence A099936 A092506 A127063
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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 17 2003
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EXTENSIONS
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More terms from David Wasserman (wasserma(AT)spawar.navy.mil), Jun 20 2005
Terms 17-22 computed by Karl Hovekamp, sent by David Wasserman (dwasserm(AT)earthlink.net), Dec 19 2006
More terms from Karl Hovekamp (karl.hovekamp(AT)web.de), Jan 01 2007
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