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A238854 Largest right-truncatable, 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 (list; graph; refs; listen; history; text; internal format)
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 right-truncatable (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 base-4 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 (m-digits 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

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Last modified June 23 18:19 EDT 2017. Contains 288668 sequences.