

A238850


Righttruncatable reversible primes in base 10.


7



2, 3, 5, 7, 31, 37, 71, 73, 79, 311, 313, 373, 733, 739, 797, 3733
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OFFSET

1,1


COMMENTS

In a general base b, a number qualifies as a member iff: (i) it is a prime, (ii) when its digits in base b are reversed, it is still a prime, and (iii) when, in base b, it has more than one digit and the least significant one is dropped, the remaining prefix has the same properties. This implies that any baseb prefix of such a number (no matter how many rightside digits are truncated, is still a righttruncatable reversible prime. Sequences of this type appear to be all finite (see A238854, A238855, and A238856, used as examples).
This particular sequence is for base b = 10.
See also A238854 for comments on a more general context.


LINKS

Table of n, a(n) for n=1..16.
Stanislav Sykora, PARI/GP scripts for genetic threads, with code and comments.


EXAMPLE

739 is a member because it is a prime and so is 937, as well as the pair (73, 37) and 7.


PROG

(PARI) See the link.


CROSSREFS

In base 16: A238851, 100: A238852, 256: A238853.
In base n: A238854 (largest), A238855 (totals), A238856 (maximum digits), A238857 (mdigit counts).
Cf. A007500, A023107, A024770, A237600, A237601, A237602.
Sequence in context: A054797 A297710 A287945 * A245064 A052014 A236255
Adjacent sequences: A238847 A238848 A238849 * A238851 A238852 A238853


KEYWORD

nonn,fini,full,base,easy


AUTHOR

Stanislav Sykora, Mar 06 2014


STATUS

approved



