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A258802 Least base b >= 2 such that prime(n) is an absolute prime in base b with at least 2 distinct digits or 0 if no such base exists. 2
0, 0, 3, 3, 5, 4, 5, 5, 4, 4, 6, 7, 7, 7, 7, 4, 8, 8, 9, 6, 9, 9, 11, 7, 7, 9, 11, 11, 13, 10, 13, 10, 12, 11, 13, 17, 14, 11, 12, 9, 16, 9, 6, 13, 15, 10, 6, 11, 19, 12, 19, 13, 11, 16, 7, 17, 19, 19, 12, 7, 16, 19, 7, 10, 13, 19, 22, 7, 19, 19, 18, 18, 21, 10 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

a(n) < prime(n)-1. This is true since prime(n) in base b > prime(n) has a single digit, prime(n) in base prime(n) is written as 10 which is not an absolute prime and prime(n) in base prime(n)-1 is written as 11 which does not have 2 distinct digits.

For 1 <= n <= 10000, A258778 differs from A258802 for 50 values of n.

Conjecture: a(n) = 0 if and only if n=1 or n=2.

LINKS

Chai Wah Wu, Table of n, a(n) for n = 1..10000

Wikipedia, Permutable prime

EXAMPLE

See example in A258778.

CROSSREFS

Cf. A003459, A258706, A258778.

Sequence in context: A201454 A008316 A290284 * A072820 A204004 A131950

Adjacent sequences:  A258799 A258800 A258801 * A258803 A258804 A258805

KEYWORD

nonn

AUTHOR

Chai Wah Wu, Jun 11 2015

STATUS

approved

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Last modified March 29 13:55 EDT 2020. Contains 333107 sequences. (Running on oeis4.)