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A238850 Right-truncatable reversible primes in base 10. 7


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

%N Right-truncatable reversible primes in base 10.

%C 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 base-b prefix of such a number (no matter how many right-side digits are truncated, is still a right-truncatable reversible prime. Sequences of this type appear to be all finite (see A238854, A238855, and A238856, used as examples).

%C This particular sequence is for base b = 10.

%C See also A238854 for comments on a more general context.

%H Stanislav Sykora, <a href="https://oeis.org/wiki/File:GeneticThreads.txt">PARI/GP scripts for genetic threads</a>, with code and comments.

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

%o (PARI) See the link.

%Y In base 16: A238851, 100: A238852, 256: A238853.

%Y In base n: A238854 (largest), A238855 (totals), A238856 (maximum digits), A238857 (m-digit counts).

%Y Cf. A007500, A023107, A024770, A237600, A237601, A237602.

%K nonn,fini,full,base,easy

%O 1,1

%A _Stanislav Sykora_, Mar 06 2014

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Last modified January 23 00:56 EST 2019. Contains 319365 sequences. (Running on oeis4.)