

A238854


Largest righttruncatable, reversible prime in base n.


8



23, 53, 449, 191, 1171, 30671, 5827, 3733, 901687, 10357, 834469, 3043427, 5430889, 4060019, 498061, 34763, 118248433, 62344463, 218555173, 4463351, 114607657, 7903613, 14523874693, 211675817, 32814697, 93375223, 162466979, 8052409793, 12006877873
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OFFSET

3,1


COMMENTS

See A238850, A238851, A238852, A238853 for the finite lists of such numbers in four bases selected as examples. A sequence conceptually similar to this one, but for righttruncatable (not reversible!) primes is A023107. The present, more restrictive, condition leads to smaller numbers which can be evaluated in reasonable time for much higher n values.


LINKS

Stanislav Sykora, Table of n, a(n) for n = 3..390
Stanislav Sykora, PARI/GP scripts for genetic threads, with code and comments.


EXAMPLE

a(4) = 53 because it is a prime which in base 4 reads 311_b4, its reverse 113_b4 (decimal 23) is also a prime, the same holds for all its base4 prefixes (31_b4 and 3_b4), and it is the largest natural having these properties.


PROG

(PARI) See the link.


CROSSREFS

Cf. Full in base 10: A238850, 16: A238851, 100: A238852, 256: A238853.
Cf. In base n: A238855 (totals), A238856 (maximum digits), A238857 (mdigits counts).
Cf. A007500, A023107, A024770, A237600, A237601, A237602.
Sequence in context: A171432 A078854 A078959 * A045345 A133986 A103006
Adjacent sequences: A238851 A238852 A238853 * A238855 A238856 A238857


KEYWORD

nonn,base,hard


AUTHOR

Stanislav Sykora, Mar 07 2014


STATUS

approved



