A065437 Smallest base relative to which the n-th prime is palindromic.

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

Harvey P. Dale, Table of n, a(n) for n = 1..1000

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

Adjacent sequences: A065434 A065435 A065436 * A065438 A065439 A065440

Keyword

base,easy,nonn

Author

Peter Bertok (peter(AT)bertok.com), Nov 23 2001

Status

approved