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 A231442 The digits of a(n) and a(n+1) taken together are the digits of a prime; least permutation of the positive integers with this property. 3

%I

%S 1,3,2,9,5,11,8,12,4,7,6,10,13,15,14,17,18,16,19,21,22,30,20,23,24,29,

%T 26,27,25,31,28,33,32,35,36,34,37,39,38,41,42,43,45,47,44,51,40,49,46,

%U 57,50,53,48,59,56,63,52,61,54,67,55,69,58,70,60,71,62,72,64,73,66,79,75,65,74,68,77

%N The digits of a(n) and a(n+1) taken together are the digits of a prime; least permutation of the positive integers with this property.

%H Lars Blomberg, <a href="/A231442/b231442.txt">Table of n, a(n) for n = 1..10000</a>

%H M. F. Hasler, in reply to E. Angelini, <a href="http://list.seqfan.eu/oldermail/seqfan/2013-November/011858.html">Two make a prime</a>, SeqFan list, Nov 09 2013

%e Start with a(1)=1. The same number cannot be used twice, so the least prime that can be made with this digit is 13, so a(2)=3.

%o (PARI) {a=1;u=0;for(n=1,99,u+=1<<a;print1(a",");for(k=1,9e9,bittest(u,k)&&next;d=Vec(Str(a,k));for(p=0,(#d)!-1, isprime(eval(concat(t=vecextract(d, numtoperm(#d, p)))))&&t[1]>"0"&&(a=k)&&next(3))))}

%Y Cf. A231433 (analog for nonnegative integers).

%K nonn,base

%O 1,2

%A _M. F. Hasler_, Nov 09 2013

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Last modified April 2 02:09 EDT 2023. Contains 361723 sequences. (Running on oeis4.)