A069867 - OEIS

A069867

Primes in which repeatedly deleting the least significant digit then the most significant digit gives a prime at every step until a single-digit prime remains.

%I #12 Dec 07 2018 17:23:39

%S 2,3,5,7,23,29,31,37,53,59,71,73,79,131,137,139,173,179,233,239,373,

%T 379,431,433,439,479,673,677,733,739,839,971,977,1319,1373,1733,2237,

%U 2239,2293,2297,2711,2713,2719,3313,3319,3371,3373,3533,3539,3593,3733

%N Primes in which repeatedly deleting the least significant digit then the most significant digit gives a prime at every step until a single-digit prime remains.

%H Michael De Vlieger, <a href="/A069867/b069867.txt">Table of n, a(n) for n = 1..440</a> (Primes p <= 5 * 10^7).

%t Select[Prime@ Range@ 512, AllTrue[FromDigits /@ Rest@ Fold[Append[#1, Delete[Last[#1], 1 - 2 Boole[OddQ@ #2]]] &, {#}, Range[Length@ # - 1]] &@ IntegerDigits[#], PrimeQ] &] (* _Michael De Vlieger_, Jan 20 2018 *)

%Y Cf. A033664, A024770, A069866.

%K base,nonn

%O 1,1

%A _Amarnath Murthy_, Apr 21 2002

%E Corrected and extended by Larry Reeves (larryr(AT)acm.org), Sep 24 2002