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A065437
Smallest base relative to which the n-th prime is palindromic.
1
3, 2, 2, 2, 10, 3, 2, 18, 3, 4, 2, 6, 5, 6, 46, 52, 4, 6, 5, 7, 2, 78, 5, 8, 8, 10, 102, 2, 5, 8, 2, 10, 136, 138, 148, 3, 7, 162, 166, 3, 178, 10, 6, 12, 6, 11, 8, 222, 8, 12, 3, 14, 12, 8, 2, 262, 268, 7, 11, 14, 282, 292, 7, 310, 2, 316, 15, 9, 346, 8, 10, 358, 366, 4, 13, 10, 388
OFFSET
1,1
COMMENTS
Subset of A016026 for primes only.
LINKS
Eric Weisstein's World of Mathematics, Palindromic Primes
EXAMPLE
71 is the 20th prime and can be written as 131 in base 7, hence a(20)=7.
MATHEMATICA
PrimeMinBase[ n_ ] := NestWhile[ # + 1 &, 2, IntegerDigits[ Prime[ n ], # ] != Reverse[ IntegerDigits[ Prime[ n ], # ] ] & ]
sbr[n_]:=Module[{k=2}, While[IntegerDigits[n, k]!=Reverse[ IntegerDigits[ n, k]], k++]; k]; Table[sbr[n], {n, Prime[Range[80]]}] (* Harvey P. Dale, Jun 07 2016 *)
CROSSREFS
Cf. A016026.
Sequence in context: A364571 A202538 A239736 * A097721 A073756 A328829
KEYWORD
base,easy,nonn
AUTHOR
Peter Bertok (peter(AT)bertok.com), Nov 23 2001
STATUS
approved